Don't know much about either to be honest. I'd provide more detail - years, condition, options, engine type and hours, where located etc. Some big factors to consider year, condition, maintenance record and where it was used (sun factor) etc
My last boat was a 2008 273 Chase and it served us well. I hope this makes sense...it's a really big, small boat. We've spent many hours feeling comfortable and safe offshore in the Keys but can still use the boat to carefully drift the edge of a flat. I think the 271 can handle any situation you're willing to put yourself and your crew through.
271 Canyon weighs 5900 pounds without engines the Robalo at 7000 pounds with power. The weight appears similar. Both are 9'6" wide The Grady is 26' 10" long to the Robalo at 27' 4" Grady lists a 20 degree deadrise at the transom to the Robalo having 23 degree....this seems to be the major difference. For the money your looking to spend sea trial both