I've been an unabashed Kirk fan for a long time. I think he is a top 5 QB in the right situation. I think these two contracts should be similar.
But if KC's contract gets into the 5 year, $145m+ range (which it may), even I don't think he's worth it. If it goes there, then the Skins were right to cut ties (although they should have done it last year, tried to get a small amount back in a trade, and started McCoy or found another QB).
JG has huge upside. That's why this deal got done at this amount. Kirk, for all I love about him, hasn't proven he can win the game that matters, and unlike JG he's had his chances to win important games. Some of that isn't Kirk. But some of it is. As a GM, I'd have a hard time forking over more for KC than for JG.
KC's agent better be careful not to outpace the market, because there are 4-5 QBs in the draft plenty of teams wouldn't mind settling for and immensely less $s.