Assuming you know your own mind (I did the same thing - I had a 686 and discovered revolvers just weren't for me - haven't missed it yet even though nothing wrong with it per se - just didn't like revolver ergos, trigger, etc) here's what I'd suggest:
Try out any semiauto you like. If friends or rental ranges don't have them this may be tricky, but at the very least hold and point them in gun stores as much as you can.
Nothing evokes more emotion pro or con than Glocks. I like 'em just fine myself but unless there is a conspiracy of unimaginable proportions, plenty of people genuinely find them uncomfortable to hold and unrewarding to shoot - just like I do revolvers and others do 1911s or CZs or whatever. Glocks are about as reliable as you can get - never had a lick of trouble from any of mine. They are of workmanlike if not stellar accuracy (although the .45s seem to do well in this regard - certainly for me), extremely easy manual of arms and extremely ubiquitous parts and service availability.
The P99 likewise has variable feedback. I wasn't too fond of the one I tried but you might be. Some reliability issues are heard of here.
Other options for hi-cap railed polymer guns may be Steyr (a very Glock-like feel but nicer trigger and some refinements elsewhere) or the XDs as you mention. I'm not a huge fan of XDs - the trigger feels funny to me (funnier than the Glock yes!) but plenty of very knowledgeable people are and you may be too. I'd also suggest you check out the Taurus 24/7 Pro models if you like an SA trigger as I do or the Millennium Pro versions if you like DAO. Very reliable, compact, extremely nicely priced, high cap and railed.
As always, best for you is the most reliable gun that meets your preferences and feels/shoots good in YOUR hand, not mine or anyone elses. Still if you try XD, Glock, Steyr and Taurus I'm pretty sure you'll find something that suits!
