Is the World Heavyweight Championship bigger then the WWE Championship?

Well I think the WWE championship isbigger than the world heavyweight championship simply because it's been around longer and more legends have held it.

The WWE championship has not existed longer than the world heavyweight championship, the world heavyweight championship has existed since it's form as the NWA world championship in 1948, WWE's championship was created under the name WWWF world heavyweight championship in 1963.
And by the looks of it, the WCW and NWA world heavyweight championship was held by quite a few legends, some of which has also held the WWE championship, therefore I would actually go as far as to say the World heavyweight championship has held by more legends than the WWE championship.

That is although if we choose to follow the physical title belt rather than by name, which is what I choose to do, therefore making the World Heavyweight championship belt the longest existing belt of the two, and the belt with most legends behind its name, at least for now, seeing that the WWE championship will most likely catch up eventually.

I think both belts are on an equal footing as far as prestige and history. Both belts are continuations of previous belts that have a long list of champions who have held it (David Arquette and Vince Russo excluded on the WHC side). I think that in the WWE's eyes, the WWE belt will always be the premire title just for the simple fact it has a longer history with the company. I agree that the spinner belt does look a little cheesy compared to the WHC belt as it does scream Cena instead of whoever else is holding it.
As far as what belt is defended last on a PPV, I don't think it matters as the last match is always booked as the percived highlight / main rivalry at the time.

I see this guy chooses to see it the same way as me, although there is one mistake you make LascoX, the WWE championship has not really changed in any "big" way, only by name and looks, but not in form of a huge company change as the World Heavyweight Championship, therefore I wouldn't say that "both belts are continuations of previous belts"

And i must admit I actually don't mind the current look of the WWE championship, yes certainly it looked a lot cooler with the attitude era belt. The WWF championship belt (Before the attitude era, the belt Shawn Michaels and many others carried around) looked very prestigious, especially with the wing kind of look.
And the WWE Undisputed championship belt, later becoming the normal WWE belt, sure as hell was perhaps the greatest look it had if you ask me, but I still must admit I do not mind the current belt, and I didn't mind it spinning in the past, just happy it doesn't anymore.