At this transition point, the problem is amplified by the fact that on one side, you have the old/current, the 1.6.4. Almost all the modders have kissed it goodbye and moved onto 1.7/1.8 thus, definitely no improvements, possibly some bug fixes but in some cases, none of those whatsoever. Thus, what you have is what you WILL have moving forward.Yeah, that was the impression I got as well. The big change was the Item ID thing, and the second biggest thing was the biome generation (which doesn't affect this pack at all, obviously). I just don't see either of those things really affecting this pack in the slightest. Therefore, it seems like we are trading a lot for basically nothing. And to everyone saying "Yeah, switch to 1.7.10, it'll have less bugs." This is just not the case. 1.7.10 and the mods associated it are just crazy buggy. Buggy buggy buggy. Every mod I've ever used in 1.7.10 has been just crazy buggy with world crashing/world corrupting bugs. And there are at least a couple of mods that this pack uses that aren't available (yet) for 1.7.10.
TBH, I just don't get why anyone would want to switch over. Maybe for CL 2 or something, sure. But yeah, for CL, I just think that there are literally no good reasons to switch, and lots of good reasons to stay in 1.6.4. I could be wrong. I don't claim to know everything about the two versions. Maybe there are some fixes in 1.7.10 that specifically fix some of the bugs in CL. If so, yeah, totally, lets go to 1.7.10. But if not, I just don't see any advantage at all to switching.
On the other side, the modders are actively working on 1.7, possibly 1.8 and thus, the future (emphasis on FUTURE) will hold much greater promise in time since they are actively adding new features as well as fixing bugs on a constant basis and getting used to forge and forge itself is going through alot of changes internally to be compatible for 1.7, and 1.8, thus you have two camps working independently of each other, both creating bugs and fixing them that it's going to take a while for some stability to come to pass.
As I stated above, my experience is definitely a 20-30 fps drop at this moment tho a direct comparison is pretty much out of the question since things are so different. my experience tho is that 1.7 (haven't played 1.8 yet) is just too immature to enjoy too much at this time. It's definitely within forge and the mods themselves that this problem lies tho. Vanilla 1.7.2 and 1.7.10 work just fine on my box.