Poor kashmiran. All he wanted was some advice on which shows were best to get and instead he gets a bunch of lectures about buying vs. downloading, and "my dick is bigger than yours" audiophile posturing.
My apologies kashmiran.
If it's not too late to be of use, I'll give you my opinion of the 5 shows you listed to choose from.
1. March 11, 1975, Long Beach: This is the first show of the 5 that you should get, but on one condition...make sure it is the Godfatherecords release "The American Return" and NOT the Empress Valley or Eelgrass releases, as they run too fast. The Godfather release has the soundboard tape at correct speed in excellent sound; for some reason the 1975 tour soundboards all sound better than the 1973 and 1977 sbds. Another plus you get with the Godfather version is better patching of the gaps with Mike Millard's tape, better fades into and out of the discs, better artwork...and, as a bonus, the hilariously inept liner notes of Paul deLuxe, who, it seems, has only a passing relationship with the English language. The cover of this release features a photo of Jimmy playing the doubleneck against the backdrop of the American flag.
And while the band's performance doesn't top the next night in Long Beach, nor the other March 75 dates, it's good enough...1975 found Zeppelin getting their funk on and the funkiness usually reached a peak in the Crunge/Theremin interlude between WWL and Black Dog. March 11, '75 Long Beach provides a cool example of that, along with some great Plantations. Add in the excellent sound, and it's clear this is the first choice...but only if it's the speed-corrected Godfatherecords release.
2. February 28, 1975, Baton Rouge: Another great sounding 75 sbd, with good to great versions of nearly every song, including the first use of Woodstock in Dazed & Confused...well, at least until a tape of the '75 Houston show surfaces. Only Stairway and Black Dog are subpar. I have EVSD's "Rampaging Cajun", which I believe is the one you said your store had.
P.S. If your record store doesn't have the Godfatherecords version of the 3-11-75 Long Beach sbd, then Baton Rouge moves up to the #1 slot and Long Beach moves down to the #3 or 4 slot; unless there's another speed-corrected version that they have.
3. June 7, 1977, New York: Now if your store did have the Godfatherecords version of the 3-11-75 sbd, and you got that first, then to avoid 1975 fatigue, you could get this second and then get the '75 Baton Rouge show. The version I have is Empress Valley's "Magical Sound Boogie", and once you get used to the dry sound of the '77 sbds, you'll find this is a pretty good show, especially if you prefer the '77 setlists to '75.
It's the opening night of a 6 show stand at Madison Square Garden, and from all accounts the atmosphere was electric. Of course, that's the one thing sbds can't capture: atmosphere. But you do get great versions of IMTOD, Achilles and the acoustic set in sbd sound. No Quarter includes Nutrocker. Only Kashmir and Rock n Roll fall apart, and surprise surprise, neither was Jimmy's fault. Jones and Bonzo were at fault in Kashmir and Plant came in too soon in Rock and Roll. Another drawback is that there are gaps and cuts in the sbd tape.
But all in all, an above average 1977 show from the run of Madison Square Garden shows, from which NO decent quality audience tape exists. LA had Mike Millard; where was New York's equivalent?
4. May 14, 1973, New Orleans: As noted before, you got the date wrong for this show. My version of this show is Godfatherecords "The Drag Queen of New Orleans", which is how Plant introduces Bonham before Moby Dick. It's a typical sounding 1973 sbd, maybe better in some spots(Jonesey's keyboards really come through in No Quarter and Jimmy's guitar does have that wondrous 73 tone), with some, but not all, of the gaps patched with an average audience tape. In fact, the opening two minutes of the show is the audience tape...the sbd doesn't kick in until the middle of Rock n Roll.
But worse, Communication Breakdown cuts out before the end...right when the band was getting into a funky groove. So all in all, a decent early-US leg 1973 show, but not as essential as the other shows on your list, so I would wait until you got the others before you got this show.
As usual with a Godfatherecords release, you get excellent packaging and photos(for way cheaper than EVSD and other labels) coupled with the nonsensical musings of Paul DeLuxe.
5. March 14, 1975, San Diego: You mentioned "Conspiracy Theory", which is EVSD's release of the sbd from the heretofore unknown SECOND San Diego show of March 14, 1975. Alas, I just don't find it a good show, so I rarely feel like putting it on. For one thing, it suffers by coming between the AMAZING 3-12-75 Long Beach show and the Seattle/Vancouver bacchanals. And it's not complete...it's missing the WWL/Crunge/Theremin/Black Dog encore, which often was one of the highlights of the tour. I would recommend this for completists only. The cover features a photo from one of the Earl's court shows, not San Diego.
There you have it kashmiran...hope it's of some use to you.