Custom-fitted G20's without a doubt, but then again I am heavily biased as that's my current club of choice.I've heard the G25 are not much different to the G20. Golfgeardirect have the G20's at £379 and are doing £50 off all irons this week, which would be a pretty amazing deal!
Obviously it's down to feel, but which one's would you pick and why?
And there's a world of difference between the G20 and G25 irons (it's the G15 > G20 move that was mainly cosmetic) and you may well find that you get on with the latter more than the former, but you'll need to hit them to find out.
One thing I will say is the CFS shafts in the G20/G25 irons are a bit strange. There's very little difference in real world terms between the Regular and the Stiff, at least until you get to the longer irons.
If you go Ping, get custom-fitted and try to make sure you get to hit longer irons than just the 7 they usually use in their fitting carts.