Lang has been around forever and has always had a good solid reputation. Shirley has been around for awhile now, and has a great reputation for high quality at decent prices (although you may have to wait two years to get one). Can’t go wrong with either. Both hold their value well if you ever want to sell.
Glenn’s is an unknown pit builder. Never heard of them until you posted. Doesn’t mean they aren’t high quality. From the quick look at their website, they look like well thought out pits.
Another reverse flow newish pit maker it TMG pits. They are starting to build a decent reputation on their pits. Might be worth checking out.
Not knowing where you live, I always recommend going with a close by shop if one of these fits the bill. Lang is about 2.5 hours from me, which would mean I could go pick up at the factory and shake hands with Mr. Lang himself.