I have never used a Rena filter, but I have read nothing but good things and reviews on them. As far as the 350 goes I used to run them on a few tanks. Never had any problems with them. I actually ran the 400's but same difference. My only issue with them was they are louder then my current AC110s. Other then that they were great filters.
I'd say if you wanted the Rena go get it. A can is always better then a hob
filter plus you get the added bio filtration that is offered when using a can. Really I'd get both since you already have it, ya might as well keep it.