Disregarding launching and loading issues, both tandems work well as a solo craft when properly ballasted. Both handle quite differently than the Revo 11 because of their additional weight and size. In terms of performance, the Oasis is the better solo boat. It cruises faster, quieter, smoother, requires less ballast, and ironically is truly the "big sister" boat to the Revo 11. Take a look at the bow and stern side-by-side comparison below and see if you can tell which is which. The Outfitter isn't even close (neither is the Revo 13, frankly).
The Outfitter would be worthy of consideration if fishing rather than cruising is a priority or if space is at a premium. Otherwise, the Oasis would be the overwhelming choice IMO. Here's why:
Hobie makes 15 Mirage Drive boats, 5 of which are tandems. Each model excels at certain things (weight, storage, seaworthiness, speed/range, smooth ride, etc. etc). But if you look at the "best of show", the most versatile, the Oasis is it. It has no weaknesses, can transport a refrigerator, has outstanding stability, good speed, great seaworthiness, is a solid fishing platform, loads reasonably well overhead by one person and is excellent as an all around tandem and solo
performer. I have hundreds of hours solo time in this boat and solo is my favorite configuration. I feel confident launching it in any water (that I would launch in ) without restriction.
Sitting in the back seat (solo) with about 55# ballast in the nose, the sensation is like operating a locomotive -- powerful, resolute and sure footed. Operating from the front seat (current models all have dual controls) and about 25# of stern ballast, the boat feels like an F-4 Phantom cockpit -- nimble yet with a lot of authority -- I thoroughly enjoy it! (By comparison, the Revo 11 feels more like a little sports car).
The Outfitter, being shorter, requires more ballast, pounds in chop , is slower, noisier and less pleasurable to operate and is wetter in adverse conditions (which you might get caught in).
If you get an opportunity to demo both boats you'll feel the difference instantly. (bring your ballast). Actually the Oasis handles fairly well without ballast from the front seat in smooth water (haven't tried the Outfitter from the front seat).
Make sure you can handle the seawall problem before you settle on a tandem though!