As has been pointed out, SmackDown! is a more straightforward wrestling show than Raw is. SD! has had a simple but very effective formula for quite a while now. The formula typically consists of a couple of main promo segments, a scattering of brief backstage promo segments, and usually 5 matches with 2 or 3 of them being extremely good. Vince usually stays out of the way on SD! and lets people do their jobs. He doesn't try to micromanage every single aspect of the show the way he normally does for Raw, thereby driving himself and everyone else crazy. SD! isn't usually live and so it doesn't have the same type of energy that Raw has going for it. Live shows just generate an energy that taped shows don't. It's just how it is even if you don't read spoilers.
Raw is generally the show where everything happens. It's the WWE's flagship show, it's live almost every Monday and it's the show more people think of when they think of WWE. It's where the celebs come to, it's where a lot of ppv hype can come from, etc.
The brand exclusivity is all but gone now and, personally, I've got no problem with that. I like the idea that I can turn on Raw and see Daniel Bryan get into a confrontation with Michael Cole. I like turning on SD! and seeing Dolph Ziggler wrestling against Sheamus. I also like the fact that WWE has put more emphasis on SD! by just the simple act of having SD! stars regularly show up on Raw each Monday.
As for the one I get the most sheer enjoyment out of, I'd say that it's too close to call. There's some fun stuff happening on both shows. Both shows have got talented guys on the roster. CM Punk is the WWE Champion, Mark Henry has been the biggest surprise of 2011, John Cena at least looks to be on the slow build to a heel turn, Daniel Bryan looks to be on a slow build to clashing with Mark Henry at WM 28, Dolph Ziggler looks to be headed for the main event picture anytime, Cody Rhodes continues to be one of the best young heels going today & his feud with Booker T has some real promise, Zack Ryder is all but assured to be the next United States Champion, Wade Barrett is back on track to being one of the best young guys on the WWE roster, it's heavily rumored that Chris Jericho will be returning in less than a month, etc.