Although I haven't actually seen or tried a Yamaha alto in person (but only in catalogues), typically they look very well designed and built.
Currently in the UK, the Buffet alto is the less expensive alto compared to the Yamaha (going by Howarth's pricing) and the Buffet has the LH Ab/Eb lever and floor spike as standard - the Yamaha lacks the LH Ab/Eb and floor spike and will thus need a sling as means of support.
Amati have in the last few years copied the Buffet/Yamaha design, though they still have the older Selmer-style ring key (and only to low E) model listed: