We looked at both, and eventually went with a Swanstone 36" neo-angle enclosure from Home Depot. (I forget what that cost five years ago, but it was not as much as $1,800.)
You asked for pros/cons each way, and here's what we decided:
There are, as far as we can tell, exactly three advantages for tile over a prefabricated enclosure:
1. With tile, you can make your shower any shape and size you like. If you need to cram it into a weird space, for example, this can be a tremendous advantage. Prefabs, OTOH, are only available in specific shapes and sizes.
2. Appearance. If you like the look of tile, or granite, etc., then there is no way a prefab enclosure can measure up. Prefabs are available in a wide range of materials, finishes, and colors, but nowhere near the selection of tiles.
3. If you accidentally whack your tile shower with the screw gun, or whatever, and chip or break a tile, you can probably replace just that tile. If the same thing happens with a prefab, you could be looking at having to replace the entire enclosure.
By contrast, there are many advantages to prefab over tile:
1. For an enclosure of the same size, a correctly executed tile installation will weigh considerably more than any prefab. Of course, prefab weight varies widely as well -- a Corian enclosure will weigh more than a fiberglass one, for instance. But all will be less than tile.
2. The interlocking/overlapping nature of prefab components generally means a leak-free, water-tight installation in almost all cases. There are very few seams to leak or seal, and the one- or two-piece nature of them means leaks, if they can even happen, will be in one or two spots, which can get extra treatment in the underlayment. Tile, OTOH, can leak at the grout lines. This means you need to have a second, water-tight layer behind/underneath the tiles, usually cement-board or the like.
3. Buses move, creak, and flex. No matter how stiff you try to make the foundation of your enclosure, there will be movement. For this reason, adhesives, mastic, and even the grout in a tile shower needs to have flexibility, usually achieved with a latex admixture. Even so, the potential exists for grout cracking down the road, and even tile adhesive failures. In any case, expect at minimum to have to maintain the grout periodically. With no grout and a massive adhesive surface area, prefabs do not have this problem.
4. We find the prefab much easier to keep clean. There are no grout lines to retain dirt, and the walls of our Swanstone are mirror flat and smooth. We clean the shower walls after each use with the same squeegee we use to clean the glass part of the enclosure, and I think we've had to get in there and actually scrub anything with cleanser maybe five times in that many years, and that's with daily use. The pan, which has a pebbled non-skid surface, is a bit harder, requiring a bristle brush periodically, but still less effort (IMO) than grouted tile. I think the non-skid is actually also a safer surface than even Jack's "more grout lines" tile.
5. Less maintenance. I've recaulked our three seams exactly once in five years, and that's in a moving bus. The last tile shower I had, in a condo, I think I was in there maintaining grout lines and caulking seams every year or two. Also, the glass edging joins the enclosure along a flat surface, so that, too, is an easy bead of caulk. Where the edging meets tile, you have little valleys at the grout lines, requiring a more skilled touch with the caulk.
So, that was our thought process. I have to say, for us the issue of appearance was solved by going with the Swanstone, which looks nearly as nice as tile, at least on the walls. The pan a little less so, but your eye does not really go there.
Hope that helps.