I like seimitsu however people talk a ton about seimitsu being awsome for shooters, that nothing tops it and whatever, I personally don't see it. I have tried every type of game I usually play with it and although is good and it does the job right, I just don't see advantage that it has over a sanwa.
Sanwa feels just so damn nice, specially with the octagonal gate, it's like a dreamboat of directions all freaking ready, I don;t get that sensation from seimitsu, but I will admit that they do feel awsome the first couple months when the inner plastic that holds the semi circled bushing hasn't worned down the directional grooves on the base underneath it.
THe important thing to notice is that is all about prefference 'cause is just nicks and nacks for different types of taste, in truth both brands are excellent and either will perform just fine in any candy cabinet.
LIke everyone else here has recommended I would suggest the JLF from Sanwa, and the LS32 from Seimitsu but if the candy has a wire harness for the stick then you should get the LS40 which is pretty much the LS32 with a PCB, but everything else is pretty much identical, ok maybe the plate it has is different but other than that they're the same.
Incidentally, going back to the Happs refference, I shit you not when I tell you that I do better on a super on any game that I regulary play than with any other stick, can't say I blame you for not wanting to put it in a candy, it's just not right which is why I still bother with having woodies. I think is due to the tighter spring, the quick return to center, I use the counterweight in my favor for quickness and instant react, like dashing and doing tippy toes in shooters, the stern spring causes the stick to come back quiclky when is barely tapped which grants you a quicker chance to do it again and again fooling bullets left and right. For fighters is a beast 'cause you have the biggest amount of freedom and comepletely cornerless where is your precision that counts, not your training wheels. Happs will always be dear to me, I wouldn't have gotten in this hobby if it wasn't for them.
Like I said either choice is fine, just pick one of the two jp brands and later you can get another set and see what you like best.
