49 keys are the most frequently used midi keyboards if you work at home with computer. No problems with transposition, etc Plus many of them are cheaper.
Best build quality I think goes to Arturia Laboratory, alu and wood sides. Novation SL MkII is also good. Worst to cheap M-Audio Axiom (non-pro) and Behringer.
I use the KORG K49, good bang for buck if you don't need heavy weighted keys. It has "semi"-weighted synth action keys, with good sensors for the velocity. My old Roland became very inconsistant over a couple of years, but the KORG still gives me the same response curve for the full range. Sure, it ain't near a NORD in quality, but it gets the job done. Much better than Behringer crap. It's discontinued, but you should be able to pick one up for nothing.
I didn't realize you were so into music Vitaliy. Noticed the music-related gear threads. I'm getting back into it after good break. I'm thinking of getting a Yamaha weighted keyboard for my control surface. (I use a Korg) I don't use alot of knobs and other faders for the sound design. I don't understand all the details of the parameters for those filters in software. But i am into recording accoustic instruments, soft-synths and vocals. Are you into mic-pres and other hardware too?
We have quite unknown film about V.V. Andreev (guy who made modern balalaika), very interesting to see (quility is not good, but love main theme, look for next parts yourself)
Had been on first limited showcase with director, actors etc, in 1987 :-)