Overall it's one of my new favorites but I still prefer honeycrisp due to it being juicier and a little sweeter in my opinion. In my local market price was identical.....both being pretty expensive.

As I understand it is a cross between honeycrisp and zestar. I've never had zestar but when researching what I'd like to plant next year I was wondering about Zestar as an early season apple but Pristine is pretty high on my list due to its disease resistence. What does zestar taste like in comparison to Honeycrisp and sweet tango?

I'm planting William's Pride next year for all the reasons you mentioned. WP is earlier than Zestar and more resistant to diseases than Pristine and Zestar. It is also said to be the best flavored of all the DR varieties and keeps about 50% longer than Pristine. WP is also a pretty apple although Zestar is nice too.
WP also seemed to be a bit more versatile in use than most early apples from my research.

As for Sweet Tango I believe it's a managed variety at this point and only certain growers are licenced to grow it. I don't think it can be grown in the backyard.

But compared to a really sweet apple like Golden Russet or Envy, they don't seem to me to have a lot of sugar and the acidity seems pretty one-dimensional.

I have a brix meter that I've never used. One of these days I need to break it out and measure some store-bought honeycrisp.

Does anybody have brix comparisons between it and other apples?

Golden Russet is a very sweet apple, often in the 20-22 brix range. It is also a much later apple, which gives it a chance to build up the sugars. I picked a few early this past weekend at a PYO orchard (the same one I got 30 lbs of 20+ brix GR last year). Given that this was a month early, I wasn't sure what to expect. So far, I've had 2 of them and both had black seeds (so they are at least somewhat ripe). One was ~14 brix and OK and the other was 16+ brix and pretty good. Not as good as those from early November, but they are better than most to my palate. Of course, my older daughter and wife both said "ugh, so dry", while my younger daughter (who normally doesn't like apples much) wanted more.

I haven't had any Envy apples- I'll need to keep an eye out for them. SweeTango is a very good apple. It definitely has more sugar than Honeycrisp. I got a couple batches of ST at the grocery store in late 2012 and most were in the high teens, with one hitting 20 brix.

I've eaten Envy apples before. I remember the flavor being quite good but the texture wasn't as good as Honeycrisp

Envy in good condition has a crisp texture that I think most would consider much better than average. They keep really well, but with age the texture takes a big hit and the flavor remains incredibly sweet but becomes insipid.

Bob, thanks for your notes. They accord very well with my subjective experiences and what I might expect.

I've eaten Envy apples before. I remember the flavor being quite good but the texture wasn't as good as Honeycrisp