Before I knew as much as I know now, I almost bought a 155 bowfront. The deal fell through thanks to Ebay.
Now that I have a 180 (2 feet wide all the way across), I realize that having the extra width to work with all the way across is great. Additionally, if you want a nice canopy to hide MH lighting with a bowfront it will be a custom job and pretty expensive. Back when I was going to buy, the stock canopies weren't tall enough for MH lighting.
Best of luck,
Roy