Rainbow Six is a lot deeper than Gears.
A.) SWAT teams don't dive, it's not an action movie. Good movements will give you the advantage over your enemies, just like real life. The trick to Rainbow Six is to learn the maps and choke points and adjust to them.
B.)I prefer the 1st person view switching to 3rd person when leaning, I didn't like the 3rd person aspect of Gears that much.
Rainbow Six is cool because at first if you learn to shoot accurately you can do well, but then as you learn to move more efficiently the game opens up even more.