Dips? The elbows at the fold? You have to get those selvage edges lined up to avoid elbows.
If it's in your budget, invest in both the 45mm and 60mm rotary cutters. You'll use the 45mm for cutting, trimming, squaring up, etc. The blades are less expensive and easier to find. Change those blades often. Dull blades make for grumpy quilters.
The 60mm would be great for multiple layers, trimming quilt sandwiches, and more. If you can only invest in one cutter, get the 45mm and buy lots of spare blades.
I'm currently testing out the Martelli cutter and it's been great so far. Less wear and tear on my wrist.