Everything everyone here has said is absolutely true. The Gravely will give you a much better finish product and you will get more life out out it. My first mower when I ran a business pre-military was a Gravely 50" and it was a great mower, spent many hours behind it and only ever had to sharpen the blades and change the oil. Not to mention, I reckon that you could sell the Cub for not too much less than what you are looking to pay for the Gravely. Good Luck!
NORTHWEST FLORIDA LANDSCAPING INC.
2012 Ram 3500 Cummins Laramie
2003 F-250 7.3 Powerstroke
2013 Kubota L3200
2013 eXmark 60" Lazer Z X-series
2013 eXmark 60" Lazer Z E-series
2013 eXmark Commercial 30"
2009 eXmark Turf Tracer 48"