You know, I've seen alot of that too, and it's been hard for me to put into context how to best describes the nuances between all three. Simply put - there are differences between each of these "Specialty" type guitars. Hopefully this breakdown will help a bit:
If I could only have 1 guitar for a certain type of situation, which one would I personally go with? Scenarios that come to mind that I would recommend to other guitarists:
1. Best type to P&W (Praise and Worship)? Best type for church gigs? - Special Semi-hollow all the way. There's an "air" to it that really comes through when delay and reverb are laid on thick.
2. I'm used to bigger jazzboxes, and new to PRS. Of the three which one of the three best fits? - Special SH here too. Although smaller, I feel like the semi hollow feature really brings out a certain woodiness/airiness that traditional Jazz players would really be nostalgic of.
3. I'm more of a "S-type" player, and am new to PRS. Which one will get me closest to single coil heaven? - The MEV all the way! Of the three, this gets me almost 1:1 to this type of sound (IMO). Be mindful though, my MEV has a swamp ash back and maple neck, and may contribute to the sound I'm hearing. For "T-type" sounds, the 5th position split or 4th position (with split treble pickup) on all three will get you what you're looking for.
4. I'm a sucker for a good chugg. Which of the three can best hold down the heavy rifts? -- Again the MEV wins here. The woods allow me to better scoop my sounds, lows are deep and full, but the HIGHS are "spandex" tight and crisp without being too "Ice-picky".
5. I like S-type guitars, but that darn middle pickup is in the way. Can I gel with either of these three? The MEV, with the middle pickup seeming to be shifted up a bit, at least for me is out of the way for where guitarist usually come in conflict with a middle pup.
6. Dan Huff, Steve Lukather are my idols and session work is my bag. Which of the three best provides me the best ticket back to 1986? (Chef's kiss) that Studio - man positions 4 and 5 are something else. S-type but a bit "more" - creamier, rounder, meatier. This is the guitar I'd sit down with as I'm tracking "danger zone" with Kenny Rodgers.
7. Single coils can sometimes be too thin, but I have enough Humbuckers around my place. Additionally, I want something a bit different. Which one? - Close your eyes and take your pick - the MEV and Studio are a win-win no matter the choice.
Overall:
1. Are they redundant? - I'd argue no, they each have their own mojo going on. Different woods, different pickups, different sounds. TONS of potential.
2. Is there one better than the other? - Absolutely not. If you've seen Jack Griffiths on Peach Guitars' YT channel, they all sounds gorgeous. I think that comes down to what you as a player are used to playing. I've heard some complain about middle pickup location, some about weight. These factors are all just personal preference. They're all winners!
3. If all but one had to go, which one of my guitars stays? Believe it or not, of all my PRS, the LAST to go of the three would be the MEV. Just because it's a rare bird - 2 year build time, ash back, maple neck, and has the 250/500k switch that's no longer available. Of all my PRS's though, I've be torn between my Custom 24 or Santana!