I'm not sure, wouldn't have any experience of the other models, know of a few 955's locally that put up massive hours. Probably could seem under powered if use to a 1255, but way ahead of their Doncaster cousins.
Don't know about the 955 but if they're anything like the 956's that couldn't be true. Spud men down the road have a 2wd ih 956xl that's done a sight of work, say it's been round the clock 2 or 3 times And never gave a bit of bother. Know another lad who had a case 956xl with a turbo on it that used to run a 3m Kuhn one pass with no problems. Great tractors.
The Fastrac would be valuable, but bought 2nd hand and his only tractor. The Sumo/Great Plaines drill are a great value drill in the 2nd market.