Comes down to personal opinions, but some is etched in stone...
As with any gun that's been produced for a long time there's favorable variants, and there's those to avoid like Hillary.
And in the Contenders that would generally be the Easy Open as the most favorable vintage out of all of them (circa 1981-1997). The least favorable the last version easy open frames that started post fire (approx 1997-2000) unless they have been checked/fixed. I doubt anyone except TC knows exactly where the cut-off is between these easy open frames and the last version of easy open frames that followed them (the ones with the replaceable lower breech face block). See the next question for more on this.
Some will tell you that "pre-fire" frames are superior to the newer ones; I've had both and no issues.
Probably where this comes from (along with the answer to the above question), is that the TC plant fire (March 27, 1997), besides wiping out most of their muzzle loading and stock making departments, tooling and company records was followed by them making a major design change in the easy open Contender frames. I doubt this was done because of the fire, but rather just a business decision already in the works AND production when the fire hit. Either way soon after the fire is when the last version frames with the renewable lower breech blocks came out. As with all of TC products after the fire they would have had reserve stock of some Contender frames to use up before the new change showed up in the retail market, further confusing the “when”. Even so, I have one of the last version blue EO frames that I bought new, and it is from just after mid year 1997 (#4479XX). But I have a stainless frame from the spring of 1998 that does not have the new conversion in it (#S396XX), so I don't know when the "S" frames got the conversion. TC’s new idea looked good on paper maybe, but very poor quality control (at least soon after the fire) is what is wrong with these last version frames. On this version the lower block was spot welded in, but some frames left the factory not welded at all (like mine) or so poorly welded that the blocks came loose either soon after being shot up to years later. So these frames do have issues until they have been checked and if needed fixed by TC. BTW, I hand carried mine to Tim P. (TC) at a SHOT Show, they rebuilt it under warranty and it has been a great frame ever since.
And I want one that fits as many barrel variants as possible.
As has been said, you'll get the most interchangeability of barrels (without modifications), with the standard frames, blue or stainless (not Armor Alloy frames or barrels). On the oldest barrels you might have to change the barrels locking bolts on them (from solid to split), but that's an easy fix with parts still free from TC.
The only difference I can tell is the G2 is able to set the hammer, let it down and not have to break open the gun to reset the hammer.
The only thing that irritates me about the old Contenders is having to "reset"the trigger by breaking the barrel open
And so the confusion and misinformation continues on and on... You DO NOT have to open an easy open Contender frame to reset it after you've let the hammer down for whatever reason!!! Gently squeezing the trigger guard part way WITHOUT opening the frame will reset it so you can again cock the hammer.
My hope is to get one with a rust preventative finish, and with a good trigger.
Finish: There is nothing wrong with the stainless easy open frames, or a blued one that has been hard chromed. I've never had a problem with rust, etc on any of the many blued ones I've owned either though.
Trigger: The Easy Open has a better trigger in every way than a G2, both to start with and after being tuned. So the descision is already made between them if the best trigger possible is important to you.
Have fun with your Contender.
L.