I'm actually highly optimistic about HM in that regard. It's not like you can do worse than making one of the game's key mechanics into a near-roulette that breaks the game back and forth (Typhoon, Mountain Vapor and River Mist yay). It's survival of the fittest. Not sure about IaMP though. I've heard a few that even barring decks and weather it's much better balanced and more technical than 12.3, but would be nice to hear a word from someone who's actually into it competitively.
can't say I play IaMP competitively (level-wise), and can't compare both games' balance or technical depth at high level play, either. Both are played differently, so I guess I'll point out some key differences so you or others can decide for themselves which is more technical or not :p
It seemed to me that SWR attempted to deal with "frustration factors" in IaMP and/or be easier to get into or attract new players, so, going over said "frustration factors" (which, like stated before, shouldn't affect high-level play)..
- combos: from a beginner's standpoint, it probably is nice to feel able to perform and watch the same combos he/she see people using often. Also, not having to worry about knowing or memorizing or deciding which combo you should use for which range (under the risk of dropping the combo or whiffing your attacks and be punished or being at frame disadvantage on block), or which commands to input, or which timing to cancel or juggle your opponent with. A number of games have incorporated such feature in them. (combos which are actually sub-optimal but easy to use and obvious enough for beginners to focus their attention to)
- supers: beginners may or may not have a difficulty executing commands for supers, in wakeups/combos/reversals/any other situation, in a way that this could cost them rounds or matches; being able to easily and reliably use a counter super (say, Youmu's counter super, Reimu's pillar, etc), or to make comebacks if you manage to dial-a (but not limited to) into a lvl 5 super (people may, of course, find better alternatives when possible, to 5 card supers) with improved graphics should feel rewarding.
- meter usage: it's bad in both games to use all of your spirit meter, but in IaMP, it's worse (spirit meter refills slower and has to be refilled to 100%, you lose air block, can't use bullets/specials/supers, can't wrongblock and receive extra block damage, even from normals); not only you have to avoid self-draining, but you have to avoid being blockstringed if you have low spirit and your opponent doesn't, avoid air blockstrings and wrongblocking 22A/22Bs.
- spellcard declaration: beginners may find it difficult to find or create a chance to declare (or input 22D, maybe) or to judge when to declare (do it too early, and you don't get good enough sc time or super meter or HP recovery; do it too late and you risk being caught trying to declare and lose the round); the act of trying to create a chance to declare and deciding when you should declare was one part of the game's strategy; another one was how to act when one of the players have declared first (do you, as the opponent who hasn't declared yet, do the same? Or try to play defensively to time out the card? Or try to make your opponent defend himself to time out the card? Or do you try to bait his/her super? Or try to stall him/her a bit and then knockdown/bomb or create enough distance or bullets to allow you to declare too?)
- movement: namely, having to know when you should jump, when you should forward/backward dash to stop rising or falling, when to change direction (because beginners don't usually care about attack ranges or startup/recovery times), having 8-way movement helps not being caught in the air.
personally, I have a few personal frustration factors about Soku (don't remember if I mentioned them), not meant to be an objective complaint, but if it helps you understand my point of view:
- lack of melee moves to counter other character's melee moves (it feels to me that they're so unrewarding, punishable, that the game discourages me to use them, except my playstyle emphasize normals over combos); moves that were otherwise useful for initiating blockstrings or punishing escape attempts (for example, Yuyuko's jA, which became j6A, Marisa's jA which became j2A) now don't net me enough frame advantage; I feel less predictable in IaMP (due to having two possible aerial melee moves instead of one -- I don't use j2As in Soku, or j6As against grounded characters, as they represent a loss of momentum if used, which leaves the jA as the only remaining option, and thus more easily counterable/blockable/escapable because I'm left with only one useful range/startup/recovery)
- high jump cancels are faster in IaMP (useful for both alleviating recovery times from bullets/specials and for blockstrings, as an option for stopping someone trying to hj through your blockstring -- which isn't in any way a dominant option, since you risk losing momentum if the opponent doesn't hj)
- so are aerial backdashes (can't use them in Soku to make opponent's melee whiff)
- I can't use bullet cover to get to the opponent at all (compare Sakuya's 214b in both games, or Yuyuko's 236a/b/c with SWR/Soku's 214b/c), bullets are either too narrow or too fast.
- bombs in IaMP can be used more than 4 times, can be used offensively (during combos), can make unsafe moves safe, can be recharged (60 points or one knockdown, as long as you didn't use a bomb for said knockdown), can be comboed after an o-bomb (it also refills the meter). Can't help feeling that they would be a waste of space in a deck, even though I rarely spend all of my deck in matches (while many people I've played against do spend all of their cards)
- once again, I can't emphasize well enough how it feels crippling for me, to grow used to normals for self-defense and countering (think about KoF 98's Ralf or Ryo, for example, though I prefer their 2002 UM versions), and then having to think "I don't have a normal to stop that other normal, it seems I should defend" which makes me defend forever in Soku (or trying to escape, which very often fails because I don't know or have memorized blockstrings). Since I have a bad memory, I can't memorize the blockstrings of other characters or the ones I'm using, and thus can't perform blockstrings or know what are the openings in theirs (to me, they all feel eternally safe on block or feel like any attack can lead into a combo that maintains the momentum -- "I thought that it would be a good opportunity to escape, but then there was this groundbounce that I didn't knew this combo had and thus I took more damage than I thought I could take"; the rules for combos in Soku aren't quite easy to deduce instinctively --, while in IaMP it's easy to see what the purpose of the attacker was, and see how much frame disadvantage I have), and can't manipulate weather too.
- tl;dr: I can't have fun mostly due to the memorization needed.
- ps: I don't see how IaMP is called a momentum-driven game, and Soku a neutral-emphasizing game, since with the former I can feel if I can escape blockstrings or not, and with the latter.. :memo: (seriously, I don't know what most alt spellcards and skill cards do, even after seeing them for years; more importantly, it was never clear to me when it was safe to escape blockstrings or not, or how to use melees in neutral game in Soku/SWR.)