Have you seen the reviews at sax.co.uk ?
Click on Sax Tests near the bottom of the list on the left.
Then Soprano Sax Tests.
I also prefer my SX90 (single neck) over the S901 for the reasons already mentioned.
As mentioned, the palm keys are more difficult, but not impossible - I use a Runyon Custom 8 mouthpiece.
The intonation is just as good as the S901 - perhaps even better on some notes - apart from the low C and B which are a little sharp.
At first the action feels slightly clunkier on the SX90, but I prefer it - apart from the bottom notes.
As mentioned in the review, octave leaps are much easier.
The SX90 does feel larger, mainly because some of the rods do stick out from the body more.
The SX90 is more free-blowing, but the advantage I find is that I can use slightly harder reeds, which improves my sound????
I only play soprano, but I must add that I'm only a hobby player, so I'm sure some far more advanced players may disagree with me on some points.
Is it possible for you to buy one/both saxes on 7/10 days approval in your area?
Good luck in your search.