Rimless looks very natural but it can be messy as well. I had one rimless tank and you could always see the dried salt from the water line around the inside edges of the top unless you kept wiping it off very frequently. If you made even the slightest splash or did anything in the tank the water made its way on the front glass so that always had to be cleaned. Heck, if one of the fish got a little to excited and made a splash it was all down the front and sides. It was also very difficult to cover the top without it looking tacky. I kept mine uncovered for a long time and you quickly find out that ANY fish is capable of jumping, just had to pray if one jumped you would find it soon enough. I finally ended up putting some screen on top though it never looked quite right. Eventually I sold the tank and replaced it with a traditional rimmed tank and I have to say im happier, but then again for a little extra work rimless does look the most natural as I said. Like anything else both has its pros and cons.
Sure in just about all the rimless pictures you see the tanks look amazing, but that is not always the case.