The Mark VII sounds great, at least in demos (I haven't seen one in person). Good choice!
I think most Marks have always had effects loops; my Mark V certainly did, and in fact, all of my Mesas have had them since the early '90s.
However, a lot of us old-schoolers prefer not to use effects loops, and even run delays and reverbs into the front of the amp. Any extra circuitry veils the sound on any amp, it's just a matter of degree.
Plenty of the best recordings in history were done with reverbs and delays going straight into the front of the amp, no loops. And that's still the case for lots of recording players (I make my living in the studio and have worked with a ton of great session folks).
So there are valid choices in having loops, or not having loops, and it's a very personal matter.
Of course my choice doesn't mean that the old school approach is for everyone. Clearly, it isn't, and there's nothing wrong with using an effects loop. It's a choice among many choices we make when we use our rigs.
The PRS amps I have - HXDA and DG30 - were costly amps, but were
purposely made without effects loops to keep the tone more pure, and I absolutely would NOT change a thing on either of those amps. They were designed to compete with vintage amps, and as far as I'm concerned, one thing necessary to accomplish that is to eliminate the idea of an effects loop and any other non-essential circuitry. Vintage amps didn't have them, and one reason they're revered is how good they are at revealing what the guitar sounds like. Eliminating the effects loop helps.
It's the same with master volumes; they add another veil to the tone. That's why the USA made Hendrix PRS amps don't have them. The less circuitry, the better for many players.
Sometimes there are incompatibilities with outboard gear that create noise using loops as well.
Dumble used to make a contraption called a Dumbleator to allow his amps' effect loops to interface with outboard gear, due to possible mismatches in impedance, levels, etc.. that create noise. This device eliminated that problem, and it was a separate, single rackspace piece of gear that was pretty costly!
I don't use the effects loops on the two Mesas I have that have them - that's by choice.
My Mesa Lone Star has a feature that allows the effect loop and global master volume to be completely switched out of the circuit. The amp sounds a lot better (to me) without the loop in the circuit, so I keep it switched out.
It's great to have the choice of removing stuff that affects tone with a switch, and it really allows the player to hear what the extra circuitry does to the tone. The Lone Star also allows an extra gain stage in the lead channel to be switched out of the circuit, and there, too, switching it out gives the amp a more transparent, less woolly tone.
Interestingly, my son has toured with a Lone Star for years with several popular bands, and I didn't previously know it, but he keeps his effects loop switched off, too.
Maybe it's genetic.
