I have owned both a Glas Signature Series, and a Poldiac but am a diehard fan of a different mod company so I believe I'm able to be completely unbiased in my opinion of the two.
The Glas is gorgeous, but likewise so is the Poldiac. They are, aesthetically, two of the favorite mods I've owned. The machining on the Glas is a bit superior and the button is downright incredible but that's a "to each, their own" kind of thing to me.
Performance is where I found the biggest difference. On the two devices, I used (pretty consistently) a Tugboat v2 with a Pour Boy Customs comp cap. My go-to builds are either 20g Royal Wires, dual 5 wrap continuous on a 9/64 drill bit, which ohms out to around.08, give or take, and 22g Royal Wires, continuous dual parallel, 5 wraps on a 9/64 drill bit, which ohms out to around the same.08 or very slightly lower, with a faster ramp time.
That said, the Poldiac absolutely cannot handle those builds. It doesn't even hot button, it hot mods. The entire tube is on fire and I can't even take a decent four second rip. Before anyone suggests cleanliness of the mod as the reason, I can assure you that my mods are kept meticulously clean.
The Glass handled any build I threw at it. Flat out, hands down, anything. Now, that's not to say that it was hitting as hard as a legit competition mod, but it handled the builds and gave me a very satisfying vape. The lowest build I ever threw at it was an 18g Hotwires, continuous 5 wrap on a 9/64 that came out to .06 ohms, and still no hot button issues.
Neither mod was/is a competition mod but I did love them for what they were, beautiful pieces of art.
I still own the Poldiac, though it gets as minimal use as you can imagine. I've tried to sell it many times but it's never garnered any real interest. The Glas, I traded for a Shock and Awe from Avid Lyfe and have never regretted it, though I do believe I will reacquire a Glas again. Once I sell the Poldiac, I doubt I will ever consider getting another.
So that's my way too long of a comparison between the two.