Where I train, we're encouraged to do the more flowing style, after we have learned the technique (generally) first.
Leading the uke really doesn't have to do with a majical wave of the hand. It can be done with or without touch. If it's done without touch it is done by leading the uke. So if the uke attacks by grabbing, instead of waiting for them to get a good strong grip and blocking their motion, you move your hand away right before uke comes into contact. If uke is commited they will continue to try to grab your hand. From what I know, uke has to be committed for this work and can't just be standing there. If it's done with touch, you move as soon as contact is made and let the uke do all the work with his momentum from his attack. Basically, either way all you are doing is taking uke's attack, extending it beyond the point of contact and redirecting it into your choosen technique.
I like to train statically to learn to work with uke's grip and learn to do a technique generally. Now that I'm 3rd kyu, I'm encouraged to move away from being static.
My sensei encourages fluid technique from day one, although some days will train one over the other.