I have a few router tables in the shop, and they all have their pros and cons - Here's my thoughts:
I have a Jessem rout-r-lift - With a router lift, you get easy height adjustment, done from above the table, and the router stays locked in the position you moved it to. On my model, I can remove a round insert, and change bits from above the table. I have a quick release collet on mine, BTW. On the other side, you have to make sure that the insert is dead flat with the table around it. And it also helps to make sure your feed rate, or the weight of the router doesn''t cause the axis of the bit to be off center. In addition, the router lift costs $$$ -- Which may or may not be a big deal.
On a fixxed top router table, I know my surface is dead flat, because there's no inserts or plates to level. The router base is just mounted to the bottom of the board. I also know that the bit is perpendicular to the face, becaus of the way its mounted. The cost is very low too - I make my fixed base tops from MDF covered with shellac and wax, which is as slick as glass, and wears pretty well too. On the down side, I have to remove the router to change bits. Depending on which router you use, for example a PC690, you have to unlock, sppin, and relock the router to change heights, all from underneath, while the power switch spins around on you. Some routers make this easier though - My PC890 has a little allen key which sticks thought the top of the table, but I'm still removing it from the table to change bits though.
On another note, my router lift table is huge, giving lots of support, but making it pretty much a stationary tool. My small flat top tables are, well, small - so I can move them around the shop easy, and mount them to a bench.
So, I hope, if nothing else, I was able to muddy up the water a bit more
Seriously though, I have both types, and for a reason. Just weight the pros and cons, and see what works best for you
Best,
Gregory