Chris, this depends on a few things. My Wife and I have an Oasis and I also have an Adventure. When she goes we take the Oasis. I also use it on occasion as a solo and thoroughly enjoy it.
As a solo, the Oasis handles very well, has very good speed and carries a ton of gear if called upon. The key is to use ballast in the nose. You don't need a lot. I use about 55 lb. The Outfitter also handles well solo with ballast.
The ride is very comfortable and dry from back here:
While not fast, it's a nice sailer:
I like to use it for local clean up activities -- you can load up the front cockpit with stuff you couldn't begin to get on other kayaks! also good for dogs, kids and guests.
Here's what I use for ballast -- both lead filled. Or you can use a water bag and save the carrying.
Riding tandem works great if one of you is content to let the other one steer. This works well for us, as my wife just likes to ride and pedal. It's also a good solution if there is a big disparity in physical conditioning in that no one gets left behind.
Conversation is a little more difficult since one person is always facing the other way. And of course, if you're both independent minded, it can be hard to agree on which path to take.
The Oasis is the longer and faster of the two Hobie tandems and has a higher payload. It's also faster than the Sport when both are soloed. Maneuverability and stability are excellent.
The only issue for you may be your height, or more specifically, your leg length. If you have long legs for your height, you should try to demonstrate one first and make sure the pedal distance allows a full extension. I think it will, but it wouldn't hurt to verify this.
The Adventure is faster than the Oasis. I could see you using the tandem and your wife with an Adventure being much more compatible in cruising speed than with the Sport. The Adventure also handles wind and chop much better. Since the Adventure has a little longer cockpit (by about 1 inch) than the other boats, it would easily accommodate either of you solo, whereas you're clearly too long for the shorter Sport cockpit.
