Hi Tim
Go for the 888 Strada if you're going to be doing mainly road riding. The SP is a fantastic riding experience, but not as practical a bike. The engine/gearing combination is more suited to the track really - it needs much more clutch slip to move off from a standstill, and its top gear is actually lower than the Strada's, so its engine feels more hurried on the motorway. Moreover, the mid range grunt of the Strada (with race cans fitted) makes for a more relaxing ride. So too does the slow steering and relative stability. (Its cold start 'choke' device is a bonus too!)
The SP is always snarling and wanting to race through the revs, and it's extremely quick steering by comparison. It feels a much lighter, more 'flighty' bike, and it's much less civilised.
Steve