I stayed at both multiple times in the second half of 2015.
Both have excellent, well-stocked lounges.
The full-scale Marriott is obviously a much larger property if that makes a difference. Rooms are pretty much similar IIRC.
The Ren has a computer downstairs in the lounge. The Marriott has a full-scale business center (possibly a FedEx office or similar) near their lobby.
Big difference is the sprawling outdoor pool at the Marriott if that is important to you. The weather was quite nice when I was there and really enjoyed the pool.
Obviously more dining options at the Marriott. Plus, the Marriott is reasonable walking distance to many other eating options.
Hope this helps!