There are two ways to wrap the tubing around on a horn. The Kruspe wrap has the B-flat change valve before the first valve and Geyer wrap places it after the third.

What are the pros and cons of each, and which do you prefer?

I believe the idea behind the Geyer wrap when it was developed was to get the valves as far away from the lead pipe as possible. The theory behind it is that as the tubing of the horn gets bigger and bigger(conical)the further along the tubing you place the valves the less affect there will be going from the conical tube to the cylindrical valve tube. The Geyer wrap has wider and more gradual bends in the main tubing. The result is that the F horn side has less resistance than in a Kruspe wrap and the F and B flat horns sound more "alike" in quality.

The Kruspe wrap horns tend to have tighter tubing bends and a larger bell taper possibly resulting in a larger or darker sound characteristic.

The result of the Geyer wrap also causes the wind passage to go through the valve sets in opposite directions on the F and B flat sides which can result in an interruption in the smoothness of the air flow. You might find note changes on the F horn feel different than note changes on the Bb horn.

Paxman Horns are kind of like a Geyer Wrap with a Kruspe valve set.

I haven't done any serious practicing on this theory. I play a Kruspe wrap myself and I have played on a freinds Geyer wrap. It didn't seem to bother me at all.

I haven't seen any Geyer wraps in silver, I do not know why but it seems to be all the nickle or silver horns are Kruspe wraps. It could have to do with the kruspe wrap being a little brighter sound so they use only brass because Silver will absorb more of the attacks so you really have to stay on top of your tonging.
John

Due to the more open wrap, Geyer horns have beautiful slurs, but you will have to tongue a little harder for the attacks. I used to play a Geyer and all those soft, legato solos can be easily and beautifully done on it. The Geyer is also better to look at, with all the extra tubing out the way (me being superficial here =D) You will need more air to control the Geyer, but its low notes sound wonderful and the good Geyer horns, eg. Ricco Kuehn, have a very good high range as well

The Kruspe usually has a good strong attack and conversely, slurring is a little harder, esp. if you changed from a Geyer to a Kruspe. I own and play a Kruspe horn right now (the Geyer was my school instrument) and it took me quite a few practices to get back my slurring. I think Kruspe horns also tend to be easier to overblow than the Geyer, but maybe thats just the school horns ;p

Personally, I like Geyers better. But the Geyer wrap horns tend to be more expensive (its just a trend i noticed)