My thoughts? MUCH lighter and phenominally faster.
As you already know, all Barnes X bullets are solid copper and don't deform, so you have near 100% weight retention and fantastic penetration for all bullet weights. Thus neither bullet weight nor sectional density play as much a role as with lead core bullets. For elk and deer to 500 yds I'd go with the lightest bullet for the flattest trajectory, even if you have a BDC scope or range finding equipment and turrets. Flatter is always better when all other criteria are met.
The Barnes 300 WSM
load data shows the TTSX 130 with a MV of ~3450 FPS with a 24" tube. With a 250 yd zero this roughly equates to +/- 3 inches to 325 yds and 25 inches low at 500 yards. The TTSX 130 is devastating on both deer and elk with proper shot placement at these velocities and ranges.
It should be possible to load the TTSX 110 gr to 3700-3800 FPS in the 300 WSM for even flatter shooting. This yields a 110 gr .30 cal bullet shooting flatter than a 22-250 or 220 swift, with less than 24 inches of drop at 500 yds. This higher velocity tends to negate, or at least compensate for, the decreased mass vs the heavier (175/200) bullets travelling ~700-1000 FPS slower, from a penetration standpoint.
I'm planning to load up the 110s in my .308 Win @ 3500 FPS for Missouri whitetails. Given the penetration of these bullets at any weight I don't think I'd hesitate to use this round on elk at these ranges. Heck, people use 180 gr ballistic tips in .308, -06, and 300 WSM, and .270 140 gr BTs on Elk and even these heavier/higher SD BT bullets come apart inside the animal, decreasing penetration.
As always, the key to a good kill is shot placement. A head, neck, heart/lung, or shoulder/heart/lung shot with either the 110/130 in 300 WSM will be deadly. A faster flatter shooting round simply makes proper shot placement easier, whether you have fancy ranging equipment and scope or not. With the X bullets I don't think the heavier weight gains you much, if anything, over the lighter, much faster, flatter shooting bullets.