What are the advantages and disadvantages of both?  Many countries seem to be in favor of the bullpup design, adopting it as their army's rifle...yet most of the fighting seems to still be with conventional style weapons. Is one better than the other or is it just personal preference?

I think the main advantage of the bullpup design is how compact they are.

Some of the disadvantages I can think of include the following: The rather short sight radius on those with iron sights. Some are not able to be used by a left handed shooter without changing out parts (if at all).  The increased noise level due to the closer proximity of the ear to the chamber.  

Can you reload the mags faster?

Is there some reason that so many countries have switched?

I'd be happy to own either.

What happens when you want to shoot around a corner to your right? Do you expose your whole body? Poor design if you ask me.

Plus it's “SUPA’ UGLY”

Have only brief experience with any bullpup designs, but of those, FN's P-90 would seem to eliminate the problem of shooting left-handed. It ejects from the bottom, has the 50-round magazine on top and its selector is fully ambi, IIRC. But it sure doesn't feel right in hands that grew up with conventional longarms, and while it may not be "supa' ugly," it sure does take some getting used to! [:)]

Depends on the rifle design. Lotta bullpups that don't interest me.

The big advantage is a longer barrel in a shorter overall length weapon.  In .223 this can be very helpful when you're trying to keep the velocity high enough to properly fragment at longer ranges.

The biggest drawback IMHO is the placement of the mag.  Its always somewhere back under your face, making mag changes awkward and slow.  Additionally, in most cases, you've got to break your cheek weld and sight picture to do it.  That is, with a conventional rifle, say an AR, you can do a tactical mag change, keep one round in the chamber while you swap mags, and keep your target covered at all times.  Granted, it won't be as steady with your left changing mags and not holding the gun down, but you still can have them in your sights and put one round on the target if need be during the middle of a mag change.  With a bullpup, its possible, but difficult and awkward at best.

The right hand ejection on a bullpup also has a tendency to interfere with the shooter.  Just remember, the ejection port is very close (usually just inches below) to your face. For lefties, its almost impossible to use, for righties, you'll probably still experience a bit more smoke and noise than with a conventional rifle.  If you're right handed and have to switch to left to shoot around a corner, you've got a bit of a problem.

I like the fact that you get a longer barrel in the bullpup but I can't get over the fact that they are butt ugly.  

Another negative to the Bullpup is your face near the cycling action. Although it is rare, if there is a KABOOM you may need plastic surgery.