x2 on everything skylinerider said. His boat, the isle, is a great one. Super stable, easy to learn on, cheap, and fun. I enjoyed paddling his. Sea Eagle sent me their needlenose to review and it's quite different from the isle. The learning curve is steeper than the isle, it's a little harder to balance on, and harder to turn, but it's really fast and tracks super straight. I thought the needle nose looked stupid and couldn't imagine a boat being good without an upturned bow, but I was wrong. Both the isle and the sea eagle are different enough that they appeal to different audiences. For a first paddleboard I recommend the isle unless speed, efficiency, and distance paddled are more important to you than easy learning curve, stability, and fun factor right out of the box.
Inflatables haven't quite caught up to the performance of the rigids yet, but they're 90% there. Curt hit the nail on the head when he said if you want an inflatable you want one with a drop stitch floor. It seems like everyone and their dog is making inflatable SUPs now. At the OR show last year it seemed like every single vendor had some sort of paddleboard product to sell. RED paddleboards is sending me a couple to review this summer, and I'll include my comments then too. They're supposed to be one of the best inflatables out there.
Personally, I prefer inflatable boats because of their ease of transport and storage. That's more important to me than performance right now. They pack up to the size of a large suitcase and can be inflated in about 10 min. I recommend a little electric pump when inflating, since paddleboards need high pressures (15 psi) and it gets tiring doing that by hand. If you don't mind storing and transporting a rigid board, they can be found cheaper than inflatables and their performance is usually better.
Paddleboarding is great fun. I wasn't in love with it the first 2 hours of paddleboarding, but now I prefer it over a kayak for short 1-2 hour paddles. For more than 2 hours, the kayak is still my preference. Paddleboarding is a lot more of a workout than I thought it'd be (mainly balancing and not falling in) and I've skated, surfed, snowboarded, and windsurfed. I like the challenging aspect of it, it keeps me interested. Hope that helps.