I like BCM just fine.

My 3 simple pieces of advice are this:
1). Get a metal lower, not a polymer lower. Plenty of folks will argue against this, but plenty of others will give horror stories of those lowers failing. Why take the chance?
2). Avoid doing business with RGuns like the plague. Their products are okay (NOT high end, but usable), if & when you finally get them. They have the worst customer service I've ever encountered.
3). If you're looking at a .223/5.56 gun, go with a lower that is made for 5.56 or "multi" versus .223. It probably won't be obvious right away, but shooting the higher pressure 5.56 out of a .223 lower will cause stress damage to the lower.

If you're just planning on shooting the AR for recreational shooting, the barrel twist rate and length isn't so important (so long as you've got 16" or a tax stamp for an SBR). But, if you're looking to shoot long range, competition, or varmint hunting, the intended purpose should drive the barrel choice.

Just some thoughts.