There are a lot of people who will swear that a 300 magnum is a better elk gun than a 7mm Rem magnum and their arguments have their merits. However, I don't think that a 200 gr Accubond is going to guarantee you exit wounds. 2 cases, neither with 200 Accubonds so they're not exact comparisons but they bound your example. 1st was a spike bull I killed about 4 years ago. He was about 65 yards broadside feeding and I plugged a 225 Accubond into his ribs with a 338 Winchester with a starting MV of ~ 2900. The bull ran up the hill about 30 yards and stood, turned wobbly and crashed back down the hill. The bullet was up against the hide on the opposite side of the bull. Last year, my Dad shot a calf at about 250 yards with 180 Accubonds with a MV of ~3050. At the shot, the calf trotted about 10 yards and stood, got wobbly and crashed down the hill. We found that bullet in the shoulder on the opposite side of the elk as well.
A 300 with 200 gr Accubonds leaving ~ 2900 fps is great elk medicine, but I'm not sure that you're going to see anything different than what happend with your 7mm. I was hunting with both a 338 Win and a 7mm WSM for several years and after killing 4 or 5 elk with each, determined that it didn't seem to matter. The reaction after the shot appeared to be about the same with both guns so I started hunting exclusively with a 7mm.
Now, I will say that I'm hunting mostly in open country these days and that the 7 is performing well, however, in open country I generally have more time to shoot so I'm setting up and making good shots. If I were back hunting the thick stuff, I would consider going back to the 338 simply because when you're taking running shots or hard angle shots through brush or branches I would have more confidence in the 338 giving me a bigger and deeper wound channel. A 300 with 200 Accubonds would probably accomplish this about as well as the 338 so if I had a 300, that would be a good choice as well.
Good Luck!
CRoss