It's really just personal preference. For me, I think a 75g bow-front looks bigger than a 75g rectangular...just more surface (viewing) area on the front.
One possible downside is that the curved front glass makes it more difficult to scrape off algae - assuming you're using an old credit card or commercially available 'algae scraper'.
I agree - I love my 72G bowfront. The curved glass gives a much more elegant look than the basic rectangle tank and offers more viewing area in front. The downside is as noted above - making your own stand / hood is harder (i bought mine instead) - and depending on the angle (really only applies in odd viewing angles) , you may get some distortion / illusion with the curved glass / water playing tricks on your eyes