I have the Giraud and really like it, but I would prefer to have a trimmer that indexes off the bottom of the case instead of the shoulder. I’ve recently begun contemplating taking an arbor press and converting it into a power trimmer, but I haven’t sat down to plan the design in full yet. My perfect trimmer would be one that indexes off the base, doesn’t use cartridge specific holders like the Wilson (which I used for a long time before the Giraud and also liked) and the Giraud, and is as fast to use as the Giraud. I don’t really care about the cutter deburring and cutting, so that isn’t a concern for me.
The Giraud is very good, but if you aren’t getting perfect shoulder bump, then it is impossible for it to cut to the same overall length. Ultimately, it isn’t a real problem, and definitely not a reason to avoid buying it. It is the fastest trimmer that still gives very consistent results I know of. I think it is probably the best trimmer available right now.
The L.E. Wilson is also very good, and I agree that it is slightly more accurate due to indexing off the base as opposed to the shoulder. It is significantly slower to use than the Giraud though.
If you don’t care about speed at all and only accuracy, get the Wilson. If speed is even a minor concern, get the Giraud, I highly doubt you’d be disappointed.
The only reason I want to mess with making my own is I think I could fairly easily make an even better trimmer without blowing a fortune trying to do it, and it’s the sort of project I enjoy screwing around with.