Originally Posted by seau grateau

Head tube and seat tube angles are pretty much the same either way. The 15mm longer top tube on the 49cm Big Block is a pretty significant change, but that seems like it would be tempered slightly by the longer head tube -- raising the front end effectively reduces your reach a bit. The 46cm has the same length top tube as your current frame, but a shorter head tube, so it could wind up feeling more aggressive. Your bike seems to have a pretty low front end as is, so you might want to try bringing it up a bit if you want more comfort on longer rides. Not a bike fit expert by any means, but that's my two cents.