I have a 2004 901CDX with a 200 big block EFI.
A Nitro is a big/wide boat. Don't know enough about the construction differences between Ranger and Nitro to give you a real answer but I can comment on performance. If you buy a 901 don't skimp on horsepower. My 901 jumps right up on plane and is one of the easiest boats to drive. Top speeds range anywhere from 70-74mph(GPS) depending on load. I don't see where the weight is hurting me in any way.
If you are considering different brands I wouldn't get caught up in a weight comparison. If you have the opportunity, drive and fish in the boats your are considering. Everyone has different preferences and each boat has its +'s and -'s. I had a Savage 884 prior to my 901 and the boats are not in the same league in terms of performance. I have owned a Ranger in the past and I have only great things to day about Rangers, but as a weekend angler that has to pay for his own boat you can't beat the value for the features you get in a 901. The 901 is a great boat.
Mine is for sale if you are interested. See 2/20/07 posting on the Swap and Sell page.