I have and use gear from both brands. Most of my 'pool' kit is Oceanic and my OW kit is ScubaPro.
To service ScubaPro gear as long as you have the slip from the previous year's service then any authorized dealer would be able to take care of your gear. The warranty is only available to the original purchaser, and can only be provided by an authorized dealer.
As far as Oceanic computers are concerned I have, in many cases, seen Oceanic go above and beyond in the area of customer service. Most of these instances have gone through dealers and Oceanic has provided, in some cases, very creative solutions. The Oceanic computers are a bit more 'liberal' in their algorithm, which depending on how you view conservatism in diving, is either a pro or a con. The Oceanics are generally a bit easier to navigate through the menus then the Uwatec units.
IMHO, Scubapro has the edge when it comes to providing support to older equipment. I can still get parts for 30+ year old regulators and keep them performing as well as brand new gear.