I have the 4.5-22 lht. It has been an alright scope. I feel like the intent was to replace the amg. The glass is as good or better and so far the reliability is better. The turrets feel like shit, but are usable. I also don't love the illumination set-up but it works.
I have several burris scopes and actually like them for their reliability. The glass quality has gotten better over time. I don't have any experience with the signature hd line, but I have an xtr ii, a US made xtr iii, and an xtr pro. All have been beat on and continue to work without breaking. The glass on the xtr3 is serviceable and the pro is quite good. People bitch about the xtr2 but I sent mine in under warranty and it came back better than some razor gen 2s (depends on luck of the draw with sample variation). All continue to track reliably and hold zero after being used on match rifles for multiple seasons. (except the pro. All is good, but only used it to hunt last fall and in a fee matches so far this year.)
I don't know which way to steer you. The glass in the upper end burris scopes had become pretty good with the lht=xtr3<xtr pro. I used a razor amg for a long time and had several reliability issues. All were handled well by Vortex. I have not had the lht long, but so far so good. It has been babied so not really tested. The Burris scopes have been accidentally dropped several times, sometimes hard, and have remained reliable.
I honestly think both scopes would serve you well. Both companies are easy to deal with, but Vortex is better. Burris is very good, but the level of customer service at Vortex is exceptional, so much so that I think it could be matched, but not beat.