Well, spokes have the advantage of distributing the impact stress better, that's why you always find them on offroad bikes. Theoretically they also give the possibility of adjusting the wheel geometry should it be needed, by loosening/tensing up some of the spokes (after you've hit something while offroading, the wheel might not break, due to the spikes, but can be out-of-plane etc). On the other hand, alloys are stiffer, and that is better for street riding, where you do not expect your wheeles to hit obstacles at that scale. Stiffer wheels mean less energy lost while transfering engine power through the weels to the tarmac. Also, they do not allow for any change of the wheel geometry i.e., wheel is always in one plane, which is very desired , especially for higher speeds (no wheel wobbling). Hence, you do not have to worry about the spoke adjustment with alloys. It doesn't mean spoked wheels are bad for street bikes, the differences are small unless you are a racing pilot and really push the machine to the limit, but then you probably are not riding the r1100r in the first place
. The BMW boxers, apart from the GS, are in general not very handy when it comes to offroading, unless you tweak the handlebars setting etc, so unless you are thinking of doing something uncommon, like use your boxer mainly for dirt roads, just go with alloys
good luck, cheers!
