I would agree with Phadeout on the 19. The 21 also has more details, FP's, and the ability to be built with panels open (as does the 19). The VF1 Club M's are nice..but the others are probably less detailed the the Hasegawa's. The Sculpts are similar, but a little different, but nothing comes to mind on the VE, VT, VF1 Super, VF1, or VF1 Strike that I would say you can't live without...they are nice...but the Hase kits compare favorably. (I have always felt the Club M's are a little more fanciful, and the Hasegawa a little more "real"...for what thats worth. )
Oh...and the 19 also has the fold booster...and both the 19 and 21 have tons of munitions.