For what your coming off of the gixxer 6 will definitly be an improvement. My 2 cents I used to ride 600s and I got caught up in the next year new model sindrome. These things are improved every year by some one. But then again so are the liter bikes now. Take your time lok at all bikes ride as many as you can and buy the one that gives you the biggest smile when you get off it.
the gixxer 6 is the *ish! okay i might be a little biased by owning one. but for real...it's very stable, she could use a little bit more on the low end of the tach (she goes bananas between 10 and 13), but it's very good nonetheless, breaks are very good, she sounds very good even when she's stock, and her handling is a dream.
if you don't mind the forward cant of the riding position and the little more pressure on the wrists, then you're straight. it's a very good bike.
what year are you considering? cuz that makes a little difference also.
I went from a 98' FZR600 to a 02' Gixxer 600M and could not be happier. As other have said there could be a little more on the low end but all around it is an excellent bike. They do sound great and handle like a dream. With a few mods you can even make it better! I have not had the time or $$$ to do anything yet but I have a list!!!!
I would stick with Suzuki but do check everything different riders have different opinions!