eh, i'd say it really depends on WHY you're losing to spanimals.
I mean, there are some things doc can actually do better in the matchup than capfal can. That being doc can keep them out better than capfal, escape tech chasing better, has easier guarenteed damage (chaingrabs), and an easier/safer edgeguard formula.
Capfal on the other hand is better at getting in on spanimals, has better tech chasing options, can flat out combo better, covers a larger range for edgeguard, and can actually outrun both of them (he can actally outrun anybody, that's one of his perks).
So, if you're looking to play doc instead of capfal vs spanimals, it better be for something like "I cant keep get away from pressure." or "I drop too many edgeguards." Because if you're looking to change because "I have a hard time following techs" or "I cant keep them off of me", then yeah, you're setting yourself up for failure. >.>
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It's not so much that it's a "bad choice" as it is you really need a reason WHY you do it. That's the one thing I try to stress to everybody when it comes to getting good. (Hell, I stress that about getting good in ANY game)
You dont have to do what everybody does; you can do whatever in the f*ck you want to. You just better make **** sure you have a system to what you're doing and valid reasons for why you're doing it. Because if you just do s**t "just because", you're going to be stuck there for a long time.