I dont think there are any cons other then each cut is sized different. spare ribs are the biggest with St Louis then backribs. So naturally cooking times vary, but also spare ribs take up more space on a smoker, so if you have a small smoker you might wanna go st louis or baby backs. if you're doing a large number for lets say a party if your smoker is small.
As for taste the big difference would be the breed of pig ive found the ribs come from, if they are from a commercial hog the flavour will be rather neutral. but if you go for a pig like a Berkshire or compart duroc its a more flavourful pork, because they have better fat marbling ive found then the commercial pork you get from a chain grocery stores , but they are also more expensive cuts and might not be available in all areas.
also it might be harder to get spare ribs in your area not all butchers or stores carry them so you may have to special order them from your butcher whereas st louis and baby backs are generally in every grocery store and butcher. ive walked into many shops asked if they have spare ribs only to have the people look at me as if i have horns coming out of my head
also one thing i keep a close eye on when buying ribs is how much meat they have on the top of them. If you look at the rack of ribs the meat side esp stlouis or spares at the grocer and you see bones aka shiners... keep on walking dont buy them, the butcher has cut too much meat off the top of the ribs. You ideally want at least an 1/8- 1/4 of an inch of meat covering the bones on the top of the ribs im kinda serious about that.. ive pissed off a few butchers telling them that they've cut too much meat off the ribs haha anyhow hope it helps