Saddle choice for Half IM to IM distances?

I'm using a Felt Tri bike.  I'm looking at the Fizik Arione as well.  Is there a difference between the Tri model and the original model?  Did the Arione work really well for you?

I definitely love my arione.  It does conform to your body after riding on it, so it gets better as time goes by.  I am riding a road bike that sometimes has aerobars on it and sometimes doesn't.  If I had a tri bike I would probably look at the Tri model arione pretty hard.  The big difference between the two is the tri model has extra padding in the nose where you'd be sittong on in the aero position.  It also talks about it being seamless from front to rear so you can slide back and forth easy.  I'm not quite sure what they are talking about there as there are no seams on the non tri model.  The tri model has a silver cover as opposed to black leather.  Maybe you can move back and forth on it easy.  Whatever. 

You do need a good saddle but remember when you are on a trainier there isn't anywhere near the movement of standing up, sliding back and forth, angling the bike in turning so you are resting on the same sit bones a lot more than road riding.  Your bottom needs time to get used to that distance just like the rest of your body.