Is the only difference between the 350 and 350 Pro the bio-wheel?
Yes
But you might want to call and ask if they come with the "Double Quick-Disconnect Valves".
IDK if any mags are sold without them, these days? But big als doesn't mention them.
The Quick-Disconnects are invaluable to me, as I like to let the hoses go without cleaning for a few months or when gunk comes flying out. Whichever comes first. Opposed to letting the canister go for no more than 2 weeks. I like to get the junk its catching, out of the system. Which is half of my filters job... to catch stuff, so it can be removed. It does nothing for water quality.
And they make for removal and re-insallation alot easier.
Turn off
close 4 valves
twist
pull apart
lift canister off of motor
clean
replace
Tip: when assembled from the box. Cut the two hoses coming from the canister to the disconnects, at different lengths.
Makes it easy to know which hose connects to which, while your inside the cabinet.
Is it worth the extra money?
Depends
I wouldn't recommend them for anything bigger than a 55g.
Or a planted tank.
And with the flow cut way down on the output. It would be an awesome set-up for smaller tanks.
The mech/bio filtration of one of these on a 20g would be uberly ridiculously awesome. lol