I also have a Bernina 350 (among lots of other machines ). and I purchased a trolley right from the Bernina store - abiut $200 - not cheap. For my machine that I take to my quilt guild stuff I have a Tutto plus two other Tutto bags and I love them. Bought them at a big quilt show and got a terrific price. I also have other,rolling trolleys that I use periodically but I love my Tutto - instead of having to tilt the case to pull it pulls longwise with no tilting and has great wheels that turn. The handle does not telescope but just lays down flat on the case - you just lift it up and pull. The top is flat so lots of,other things can be stacked and held down with bungee cords.
A lot depends on what you can pay. The ones from Joann's are just fine but my machines don't fit - and I don't like the color choices. But I do have a friend that has one for her smaller machine that she brings to our guild and it does just fine. Like others have said, just make sure your machine fits and if it has more room for other things, like a,sewing box, etc. Or you can sit smaller cases on top and strap them down so they don't fall,off.
Sandy in Mooresville, NC