1st pressed vinyl best ones to get ?

Sometimes, but not always. And first pressing from what country? What pressing plant? On Zep 1, for example, my go-to is the US Piros ’74 era recut with the ’CC’ nomenclature in the deadwax, pressed at the Monarch factory, a cut that has been rightly touted and discussed at length on the Hoffman forum; also very good is a 3d Japanese press of the album which I happened into from a seller there. I own an early UK plum (but not the Turquoise lettered cover which was the earliest and is the most collectible), have listened to various US first pressings from different plants on my system by comparison, also have the Classic 33 and Classic 45 of Zep 1, and several other copies.
Zep II- the early US ’RL’ is the one everyone favors b/c of its punch- it was recut shortly after release and commands a fairly high price for one in fine, unmolested playing condition. But the early UK plum is comparable in different ways and the Canadian Red Label marked TG in the deadwax is also very good- cheaper, but harder to find.
Zep III- I really like the first UK plum A5/B5- earliest had Peter Grant credit on the label, but the Canadian Red Label (TG in deadwax) is an equally fine listen. None of the Zep records are "audiophile" quality so you are looking for something that shines, considering the starting point.
I did a shoot-out of Tull’s Aqualung and preferred the early US pressings to the first UK, but then, I also found that Steve Wilson’s remix (from a digitized copy of the multitrack tapes) was an essential listen-cheap, new, and readily available.
Skynyrd’s first album- my shoot-out among first on SOS label, MoFi and a couple others yielded best sound from a later, nondescript MCA "rainbow" reissue circa 1980.
Steely Dan’s Can’t Buy a Thrilll- I like the sound of the 2nd US press (orange target label) better than the first US press (black label). The Speakers Corner reissue is pretty good.
And so on. I think you really have to listen and do the comparisons- sometimes, one particular cutting will have strengths in one area and weaknesses in another. Or the magic is lost because of track to track variability of SQ on the record.
Some of this is shadings and some is listener preference and system bias- the way a mastering is EQ’d may be complementary to your system.
At the same time, I own an awful lot of first pressings, and quite a few early WLPs because they can be sonically better but it is case by case. Unfortunately given the cost of some older collectible records, it’s not easy or cheap to do the comparisons yourself. Leaving aside the "condition" problem. And it takes time. You thus rely on anecdotal reports from others. So, I’ll underscore what I said in the preceding paragraph- apart from collectability, on SQ, it is often differences, rather than one handily "beats" another. Though there is that, too, and usually you’ll find consensus among people on those, e.g. the "RL" cut of LZ II, though I’d still be just as happy with a UK plum. I have come to the conclusion that the quest for the best sounding pressing is just a variation on audiophilia- doing it with records, rather than gear. But it is fun, if you don’t mind spending the time and having 10 copies of the same damn record!

RLawry- at the time Tea was released, Island Records was still an independent company in the UK and had no U.S. counterpart till a short time later, so US territory would have been llcensed. I had to look it up (because I just can’t keep all this stuff in my head), but the UK firsts were mastered by Lee Hulko, who if memory serves, founded Sterling. It wasn’t unusual for Island UK to use a US mastering facility. I’m not commenting on your preference for the A&M over the UK pink (label presumably, not a pink rim); just questioning whether we can construct rules that predict sonic outcomes and how your rule applies in the case you cited. My rule: listen to it! I do agree that the sign-off of one or another of the legendary mastering engineers in the deadwax is a telltale for good sound. Not trying to be a prickly, just seeking clarification of your example.

xlh1- I don’t disagree with your observations about matrix information, but sometimes, there are multiple cuts made simultaneously, to supply several different pressing plants when a record is a high volume one. I know there is information about various Columbia plants pressing for Warners/Reprise and the "1" did not necessarily signify a first, although if memory serves, I think it was associated with the Santa Maria plant, which had very good output. (The "2’s" and "3’s" were cut at the same time, but went to different plants).
The Tom Port thing always stirs up controversy- I’m not going to wade into that other than to say that for a common record, I’ll often have multiple copies of the same record as well as different masterings. It does take time, though. And the pressing to pressing variations of identical records-- my suspicion is, most people are going to look for anecdotal comments (which to be meaningful, contain comparisons) to find a general consensus on "best pressing" and go with that. You must have been borderline nuts after listening to Casino Royale 50 times. I do dig Dusty, though.
PS: also agree that sometimes, a later mastering sounds better, see a couple examples I mentioned above, none of which were "audiophile" re-do's, just later, garden variety commercial pressings.