Depends on what centerpull and what sidepull you're comparing to. Most MAFAC centerpulls have more degrees of freedom-a curse and a blessing. For example, most of them you can adjust the pads not only up and down, but also the angle that the pad hits the rim. The straddle cable is adjustable on RAID's and Racers, for example, as well as the yoke cable. But that just gives you another knob to tune, which is sometimes useful.

I have two bikes that couldn't use sidepulls. All of the side pulls I tried on my Lotus Classique limitied tire size, as they "drooped" (for lack of a better term) down below the fork crown. I found that all of the material on MAFAC Competitions was at or higher than the bottom edge of the fork crown, allowing 33.3 tires with a few milllimeters to spare. On my VO Randonneur fitted with 650b wheels, Tektro 559's were a few millimeters short of reachiing the rim. MAFAC RAIDs, however, did the job. Both took more time to setup than, say, Tektro's fine sidepull offerings, but it was well worth it.

Not really more difficult, they're fairly straightforward, but take a bit more time.