Well, here’s my tuppence… I’ve heard that the holes you have to drill to install the sliding capo lower the value, while installing spikes can actually raise the value. Spikes look better IMPO. As to feel, I’ve played both, and I don’t notice either when playing, but I also don’t wrap my thumb very far. The presence of the sliding capo could help you locate the fifth fret subconsciously, but could also get in the way. If you have spikes, be careful when fretting the fifth, as you could spike your finger. I’m just thinking out loud, I’m not sure how much of this need be considered, it’s just what I’ve considered.