If you've got your toddler on/in/around the water all the time--which, let's face it, you will, you're a boater--buying is the way to go.
There's nothing fancy about the Stearns ones, but you're looking for safety, not high performance. They are a lot more comfortable than the crappy old orange Type II "compliance" life jackets I had to wear as a kid!! If my kiddos were able to nap in theirs, it tells me they were comfortable enough.
Floaty swimsuits are great for pool time when you are teaching them to swim--way better than water wings.