Depends on what you want it for?
I know with a 10 x 40 x50 scope & a bag rider fitted the HFT500 is just under the 10.5 lbs weight limit for L/R in Benchrest.
I would imagine the FTP900 would be much heavier.
There isn't anything between them accuracy wise.
The FTP900 is no longer in production.
I'd be buying an HFT500.