Here's the truth about Rotatrim: you can absolutely make as clean a cut with a skilled hand, a fresh blade, and a firmly held straight-edge. But not every time, and not forever. More importantly, it is much more difficult to keep the sheet your cutting truly square than it is when using the perfectly aligned Rotatrim. I hate that they cost $300, but there is a reason they stay in business. Rotatrim are AWESOME. If you can't justify the expense, I honestly suggest you find a community space where you can do your trimming in bulk. I don't know what your intended purpose is, but if your prints are going into a portfolio, having all of them all trimmed 1mm off is something you will notice.
That said, there are amazing deals out there on old industrial quality guillotine trimmers, the kind that used to live in every art classroom. Those can be had for $20 and can be resharpened within reason. A really sharp guillotine is good enough for me. But a $300 Rotatrim is a lifelong investment. I could be happy with either, but the Rotatrim is the best.
