I own and play saxes from bass to sopranino - but in the main I play soprano, alto and tenor. I find the bass and baritone sax to be bulky and heavy, but not that difficult to play. You just need more air and more breaths in any given musical score. I don't play them much because of the transport bulk. read more
Even a small problem can make a saxophone hard to play. Not sure if you mean bari/tenor/alto/soprano. In which case, probably soprano is the hardest to get in tune. read more
Then tenor, c-melody, and soprano. Vintage baritone saxes are not easy to play because they are hard to control. Sopranos are tricky when it comes to playing in tune and just getting notes out. tenor and c-melody are pretty easy to play. Bass is the hardest to master, definitely. read more