A lot of open / handicap racing is in place for new racers who managed to grab whatever boat was available. A perception that the open class is full of hotshots is a misnomer. Most of the hotshots are in the one design classes (like H16, F18, etc.).

That being said, I think you will learn and improve more quickly in a one design class. It's very difficult to sail an odd-ball boat in an odd-ball fleet and have any basis for comparison. Besides, you'll find that most everyone - even the 'hotshots' are very willing to help you get up to speed whether you are sailing in open class or in a one design fleet. With only a few excepted examples, our community is not big enough for people to be snobish about performance.