Well, I was looking at the stats to compare them, and there are pros and cons.
Compare: here
Pros:
You save 1 million+ coins (although I think that the +2PST will come down in price since there is a very good substitute card to the limited supply of 93 OOP Gronk).
When upgraded to 93 and compared to 93 OOP Gronk, you get +1JMP, +1 TKL, +1 HTP, +2 PWM, +2 FNM, +2 BKS, +1PST, +1PLR, +2MAN, +2ZON, +2PRS, and +1 or +2 on ALL Offensive stats (if/when he gets a pick)
Cons:
No +2 PST boost to team.
When upgraded to 93 and compared to 93 OOP Gronk, you lose -1 SPD, -1 STR, -1 AGI, -1 ACC, -1 CAT.
Doesn't look as cool without that "+2PST" label.
I want to add that I think the main priority is to get ZON to 99, so 91 Gronk will achieve 99 ZON at a lower OVR than 93 OOP Gronk. 91 Gronk will get 99 ZON at +12 training which is 103 OVR, but 93 OOP Gronk gets 99 ZON at 105 OVR. (Can someone confirm this with 93 Gronk please?)
Well, I was looking at the stats to compare them, and there are pros and cons.
Compare: here
Pros:
You save 1 million+ coins (although I think that the +2PST will come down in price since there is a very good substitute card to the limited supply of 93 OOP Gronk). When upgraded to 93 and compared to 93 OOP Gronk, you get +1JMP, +1 TKL, +1 HTP, +2 PWM, +2 FNM, +2 BKS, +1PST, +1PLR, +2MAN, +2ZON, +2PRS, and +1 or +2 on ALL Offensive stats (if/when he gets a pick) Cons:
No +2 PST boost to team. When upgraded to 93 and compared to 93 OOP Gronk, you lose -1 SPD, -1 STR, -1 AGI, -1 ACC, -1 CAT. Doesn't look as cool without that "+2PST" label. I want to add that I think the main priority is to get ZON to 99, so 91 Gronk will achieve 99 ZON at a lower OVR than 93 OOP Gronk. 91 Gronk will get 99 ZON at +12 training which is 103 OVR, but 93 OOP Gronk gets 99 ZON at 105 OVR. (Can someone confirm this with 93 Gronk please?)