I've actually never even thought of the quality of my tea. I've been drinking the very cheap Salada green tea, which is probably not the highest quality. My initial thought to seeing more expensive teas is that they had no more nutritional quality but rather fancy combinations of certain plants for the purpose of taste.
I'm not sure if the antioxidant content varies by tea. Hell, to be honest, I'm not sure sure I believe the hype - you know, " OMG LIEK FREE RADIKELS ARE ROBBING MY HEALTHZ!!!!111!1one1!" While I only understand the basic concept of what a free radical is, and don't know specifically about different antioxidants and their properties, it appeals to my intuition that simply following a reasonable diet comprised of a wide variety of unprocessed foods would be sufficient to maintain near-optimal health. Most of the people I see obsessing over antioxidants don't even know what a free radical is, so this makes me think that it's mostly a bunch of overhyped bullshit used by niche food industries like juice and tea companies to line their pockets.
Please let me know if I'm off base here, since my argument is only based on my intuition and sense.
To be honest, I've found that the best advantage to tea is drinking it before I train to increase my body temperature. Having a pre-training routine also improves my focus a lot.