Below are some general considerations for choosing an outrigger paddle but the best advice I've ever heard is to try before you buy.
Length
The right length of paddle depends not just on your height but the length of your torso, shoulder width, etc. and even your paddling style. You can refer to Kialoa's size chart. If you can afford two paddles, you might want to get one for OC1 that is an inch (or so) shorter than your OC6 paddle.
Blade surface area
The bigger the blade, the more water you can pull but also the more strength required to pull it. Women therefore tend to get smaller blades than men. A bigger blade will also work better in a team boat. If you can afford two paddles, you might want to get a smaller one for OC1 and a bigger one for OC6.
Blade Shape
Most outrigger blades have a teardrop shape. Some blades, notably most Kialoas, also have a "scoop" (convex curved surface). Manufacturers will claim that their particular variation gives you a cleaner catch/exit/pull/etc.
Composite vs Hybrid vs Wood
Composite paddles are made entirely of synthetic material (carbon fibre) and are by far the lightest. They also tend to be stiffer than wood, which can lead to shoulder problems for some paddlers.
Wood paddles have more flex than composites but are heavier. They are also more traditional and, in my opinion, look nicer (at least when they're new).
Hybrid paddles have a wood shaft and a composite blade. This makes them lighter than all wood paddles while retaining the flex.
Straight vs Bent/Wacky Shaft
Most outrigger paddles I've seen have straight shafts. However, you might have seen some paddles that have a couple of bends in the shaft. These look kind of wacky, hence the name. The idea behind the wacky shaft is that it places less strain on the wrist. If you have wrist issues, you might want to look into a wacky. All Kialoa paddles except the Lolo and Pono models have straight shafts.
Palm vs T Grip
Most outrigger paddles I've seen (and this includes all Kialoa models) have 'T' grips (the grip is a small piece of wood attached to the top of the shaft, making the grip look like the top of the letter T). The club has a few paddles with palm grips. Personally, I find the palm grip a bit more comfortable but I'm also happy with a T grip. Historical note: until the late 70's, outrigger paddles had no grips at all!
Steering Paddles
Find an experienced steerer and ask him or her for advice!