i prefer the true braided lines as i find they are more supple and cat better . ive used the fused lines and find they go "fluffy" and then they get more wind knots in the lighter classes  .. its a personal choice i suppose but id never go back to fused lines unless it was changed somehow. 

Fused/Gelspun line is generally thicker, doesnt cast as far, stiffer, furs up, soaks up more water and more drag through the water.

Braid is generally thinner, softer, same abrasion resistance, casts further, sheds water quicker, less drag in the water and sits better on spinning reels in particular. 

Very helpful, Im glad I asked. I was actually told just today, that the qualities of non fused, was in fact the benefits of fused, if that makes sense.  

or are they all rounded?

it depends on how experianced you are and how good you are with knots also. As above posted by oceanside, those pros and cons are some of the factors needed to take into account when deciding. Some others are, fused tends to have a memory while it isnt broken in. It does take a fair while for it to be broken in and become supple, but by then it will get fluffy and have a worn look. Like when you have a mono when its a lil tight on the spool, it tends to have curls in the line, fused will do the same for a fair while. Also with knots, you can pretty much use mono knots with fused. You could say they're an in between of mono and braid. Because they're fused, they do tend to be somewhat be a lil water resistant in the new state, so washing your spool after a fish becomes a problem as you cannot wash the line thoroughly as its pretty water tight unlike normal braid which soaks water. I suppose you can think of it like rubbing vaseline on your line, it wears off over time. The times water does get logged by fused its also doesnt evaporate as quickly because of how water tight it would be when its fairly new. Fused braids are like taking a lighter to a pair of nylon clothing, it shrinks and melts threads together. I reckon they do have more abrasion resistance than your standard braids. I do recommend using fireline to those that are new to braids but still cant get the hang of standard braids, so using fireline would be a good transition into standard braids. Normal braids can be flat or round. Its just personal preferance. Flat braids are less smooth and do dig into your spool of line a bit, but for the trade, you get more line capacity. There's no right or wrong, its all personal preferance. If you prefer mono and braids scare you because of how different it is and all the new things you're gonna have to learn, use fused and give youself time as it will become like a standard braid over time, only abit fluffy like a hairy hobo being electrocuted.
I've used fireline as my first braid and when i was used to it, i changed over with more confident. I still have fused lines on some reels here at home.

not.

Much appreciated, I'm steering away from fused... and the real freaky thing is, i was only just talking to friend a little while ago and he gave me a new spool of fused fireline - 300 yds. Once again, thanks very much. 

yea i know not all fireline are fused, just when i think of fused its first thing to pop in my head. Sometimes i say fireline when i mean to just say fused braid, Reflex lol, they are pretty much the most well known fused lines though.