Need a comfortable all mountain bindings. I can get the cartels for the price of the Spi but are they any better? They will be going on a trs btx board with salmon malamute boots.
Personally I have always went with an all aluminum baseplate for free riding, but that is just me. I have experience with the Ride RX's in the past. I had trouble with the ratchets on them. Other than that they were a decent freeride binding. I think you will be fine with either one.
I don't think the Cartels are as stiff as the SPi's if I remember correctly. So if you're looking for a freeride binding, I'd go with the SPi's. Also, in the 2009 onward bindings, the ratchets were revamped/fixed.