I would seek different 6SN7s other than GTA or GTBs. Why have you chosen GTAs to look at? If if this is your first foray into buying old stock tubes, then you may want to stick GTAs or GTBs to give you a better chance of getting a less used up tube. No guarantees of that either of course.. I didn't see the prices asked.
All other things being equal go with Sylvania. GE is probably under rated but there is precious little to recommend them, There is something called NOS but in truth I think it's getting rare. How has the seller advertised them ??
There are some very, very good Sylvania GTAs but the one you have shown is not one of them. Look for heavy chrome, flashing or gettering as it called. For example do a search of the much more costly Sylvania W (not GTW), to get an idea of the amount and type of chrome to look for on the tube. I like Sylvania on any number of price points and scarcity levels. GTAs and especially GTBs should be abundant and inexpensive. The sound is well balanced and has rounded edges , if you grant me poetic license. The GE is a decent tube better than current production in my opinion, it is unobtrusive and doesn't add or subtract much color or character to the sound. .
What would you want the tube to do if it can't be completely neutral and transparent. Do you lean towards warmth, quickness, imaging bass etc.
Let me make a general recommendation until you get tell us what you are looking for. The Sylvania 6SN7 GT 1950s bottom getter 'bad boy' style can be found at a decent price. Note that the plates have 2 rivet holes, if there are 3 that's a real bad boy, and the sellers know this as a general rule and ask a lot more for them. Do not pay for a bad boy unless it has the required 3 hole plate. I would stick with the 2 hole plated tubes for less.