When i was looking for mine i found that a lot of opinions were that 1/4" was rubbish and people should only ever buy 1/2" ones.
I couldn't justify a 1/2" one so bought the 1/4" Erbauer one. It's been great for my needs. Similar to you just routing out recesses on the back of frames for glass to sit etc. I've since used a Dewalt and Makita one, and for the same type of job i didn't notice much difference with those and mine. I think the main difference is if you try and cut into hardwoods that the bigger, more powerful units come into their own.
I'd have said that one would be fine. It gets decent reviews. Don't forget to budget for a set of router bits. I think i bought mine from Aldi which were pretty cheap.