I've owned a bunch of 7s and played some more, maybe this could help you out
Ibanez S7320 - I had a gloss black one and a flat green one made for the guitarist from Tony Danza Tapdance Extravaganza. Very nice sounding guitars, and the trem rules. I really dislike Floyds most of the time but the ZR rocks - its very stable, so you can switch into and out of drop tunings without it putting the whole thing out of tune. It feels great on your picking hand, so nice and smooth, and the adjustable tension is a nice touch. Like any double locking trem, I believe it kills the tone a bit but the S7320 seems to deal with it better than most. I hated the neck. It uses the new Wizard II profile so it is really, really square on the back with extremely pronounced shoulders and isn't even that thin. The fret work on both guitars was shoddy, which was surprising on the green one since it was made for an endorsee. Both had dead spots on the neck and just didn't play that great. Most of all, I hated how the neck felt.. but they sounded awesome. I had a stock Ibby bridge, Lundgren M7, DiMarzio Evo and a Bareknuckle Nailbomb in the bridge at different times.. the Ibby sucked but with the other ones, these things slayed.
Jackson COW 7 string - I've had two black ones and a silverburst. The older black ones had fatter necks on them that I found to be uncomfortable towards the nut but not bad at all in the higher register. The newer silverburst has a much thinner neck, with an extremely comfortable profile. My buddy's blackmachine B7 has almost exactly the same profile & thickness. The price has gone too be way too high though - these things are just not worth $1,000 new. You can bag them used for $500 for a black one to $750-800 for a silverburst or red one. They play so, so well.. awesome top end Jackson Japan finishing on the frets and neck. But, the tuners are cheap. All of mine have had tuning problems typically on the G string. Also, the headstock is huge. My silverburst's headstock broke in shipping when I sold it, so I ended up refunding the money and keeping it.. fixed the headstock and had all the frets pulled and re-done and now it is the best 7 I've ever owned. I miss having a neck pickup but can deal with it since the guitar otherwise rules so incredibly hard.
Ernie Ball Musicman Petrucci 7 - odd looking guitar sure but an awesome player. Piezos are nice, the bridge feels great, holds tuning well, and isn't a double locker so it doesn't kill the tone. Incredibly thin neck but it has a magical profile so I ordered my custom 7 string with the same thing. Loved to play it, and while it looks odd, it is just so comfortable to play. The arm carve is sweet. They are expensive though and I didn't like how it sounded - so flabby and weak with the basswood body. Sold it before swapping pickups around and I wish I'd kept it.
Petrucci BFR 7 - all the playability of the cheaper 7 string but with awesome tone. Alder body, flame maple top and a mahogany tone block or something like that - sounds AWESOME, plays awesome, looks awesome, but expensive.
ESP Custom Shop SRC-7 - Steph Carpenter's old sig model with the 7 string single coil in the neck. The biggest dog of a guitar I've ever owned, flipped it in about ten days. Tonally dead, so incredibly thin sounding, weighed a ton. Was awesome to look at but just sounded so bad and I've heard that from a lot of people who have played or owned one. Sell for $1400ish used when you find them.. not worth $500 IMO.
Schecter Hellraiser C7 - very cool guitar, awesome 7 for the price. I prefer how maple or ebony sounds though.. never played a Loomis or an ATX but that would be the way I would go if I wanted a Schecter. The necks aren't that fat, either, I thought it felt great. Sounded massive!
I've had some others but those are the big ones.. I had a Ibanez 2077XL, played the 1057 and a couple Universes, briefly played a blackmachine and had one on order etc. but my favorite out of all of them are my silverburst COW and the BFR Petrucci.
Never played one, but people seem to like 'em a lot and say they're great bang for the buck! And you could get some Duncan Blackouts to fit in there (EMG's wouldn't)
bah
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