We have two Mustang inflatables with harness MD3054 and two Mustang hydrostatic MD3153 without harnesses. We pretty much wear the hydrostatic any time sailing because they are so light and comfortable and either the ones with a harness for night or rough weather or I put on a harness WM under the hydrostatic.
And yes - as my colleague has already so wisely posted, the best safety equipment is the one you wear!
I wear two types. A Mustang Hydrostatic Inflatable or a Lotus StraitJacket. The Lotus is a non-inflatable and I use it kayaking, in cold water conditions or when wet racing. The straight jacket is warmer than the Inflatable and easier swim in. Also, since it not affected by getting immersed or wet, the Lotus is better for wet or immersing conditions.
In the summer when I am cruising and generally in warm and sunny conditions, the inflatable is more comfortable.
Whenever I am off the hook on the boat, I wear a PFD of some sort, no matter how benign the conditions.
I wear a SOSPenders auto inflatable whenever I'm on a boat, no matter the conditions. For me it's become like wearing a seat belt. I just automatically put it on. In the winter, I wear a Kayaker's vest just because I wouldn't want to take a chance on the auto vest not inflating.
What kind of boat are you racing. If you're dinghy racing, you should probably get a vest with a hydrostatic release, since that will only go off if you fall overboard, rather than a salt-pill type release that may trigger if you get soaked.
An inflatable is one of the most comfortable types of vests, even in hot weather, and if you get it with an integrated harness, will be useful on most boats in heavy weather.
One warning: Many of the integrated harness PFDs are designed for people who are 5' 8" or taller and most of the time the literature doesn't say that on the website or the catalog, but the safety instructions for the PFD will.