Tough call, parallax is the big issue between the two for me on a .22 Some matches will have very small targets in the 15-25yd range where parallax might matter. That said you can usually dial down the power to compensate, and really at 15-20yds I'm not sure I've ever felt the need for 20x or more. I probably wouldn't put either one on a dedicated .22 comp gun. If it was a trainer then sure run the exact same optic and accept the parallax issue at super short distances. For a pure 22 comp gun I'd want something with a < 25 yd parallax. It's one reason the Strike Eagle is so popular for 22's, huge elevation adjustment if you don't use the zero stop, pretty good optics, 15yd parallax and possibly the same reticle as your Razor's. Is it as optically amazing and durable as a Razor....for 1/3 of the price of course not. The athlon Midas Tac is popular for 22 as well with its 10yd parallax compared to the Ares/Cronus that are 25yd. Bushnell Match Pro - 10yd, etc. which I believe was designed specifically for NRL22 work.
On any other rifle I'd definitely say the 4.5-27x. Almost the same price, weight etc. you can always dial the 4.5-27 down to 18, but you can't dial a 3-18x up to 27x. I'd also bet the 4.5-27x is better optically at 18x than the 3-18x is. Zoom optics are almost always best optically in the middle of their power ranges compared to the extremes.
Also when everyone starts using 10-15yd parallax optics matches might get tricky and put super close shots on, so it's never a bad idea to practice beyond the limits of the parallax. Archery 3D shoots used to be that way, they'd set up a 2 yard shot and guys with all kinds of fancy sights would completely blow it.