I am new to the forum but I have a few ideas and opinions to share. With respect to the 2 rifles you had listed I would tend to lean toward the Remington. My experience with HS Precision Custom Rifles
has been nothing short of horrible. I waited 15 months for a special order 300RUM and still didn't get it. But that is just one instance. Needless to say, be prepared to wait.
OTOH, I have nothing but praise for the Rem. In particular the Sendero model. I am partial to 308 calibre so the natural choices would be 300Win/Wthby/RUM.
You may also want to look into the Weatherby AccuMark 30-378 boomer. Definitely a long range contender.