I owned an Astro-Physics 155 F7 triple apo for many years. When it came time for me to downsize due to age and weight, I kind of went through the same process.
I ended up with a Tak TSA 120 refractor and a Mewlon 210. Both are less than 20 pounds and require much lighter mounts.
If, however, you are not necessarily looking for a lighter scope but just the better ergonomics of a compound Cassegrain, then I would suggest you get a Mewlon 250. Find one with fans. They are absolutely needed.
For any deep sky object that fit in its field, a Mewlon 250 will go deeper and show deep sky objects better than the 6” refractor. The refractor will of course have a wider field of view. If you have the seeing for the moon and planets, a Mewlon 250 will pull away from a 6” refractor when the seeing gets above average. When the seeing is average both scopes will be close in showing detail but the refractor will possibly have a calmer view and the Mewlon 250 will have a less calm view but might tease (frustratingly so) with glimpses of more detail.
A Mewlon 210 will just edge-out a 6” apo on most deep sky objects that fit in its field. On the planets it will be close but I would give the nod to the 6” apo on most nights and in all kinds of seeing. On the moon it will also be close but I would give the nod to the Mewlon 210, if the seeing is just above average or better. My Mewlon 210 is one of my favorite lunar scopes. An aftermarket focuser is nice to have for a Mewlon 210 to dial in exact focus when using high power.
I can’t stress this enough. Without fans and in a cold climate, a Mewlon 210 will take a long time to acclimate. Not much of an issue for deep sky but it is for the moon and planets. My AP 155 F7 oil-spaced apo acclimated in 30-minutes in cold weather, a Mewlon 210 can take hours. If I could handle it, just that fact alone would have had me keep the AP 155.
Cooling was such an issue here in PA I added fans to my 210. They work great. But you will have to do a custom installation or come up with a different acclimation strategy for a Mewlon 210. Another reason to seek out a Mewlon 250.
No SCT has the contrast or the in-focus star images of a Mewlon. My Mewlon has remarkable contrast for a compound telescope and the stars, although not as tight as in my TSA 120 are tighter than in any of the SCTs I owned. If you go the SCT rout, a C11 Edge with TEMPest fans can be a satisfying telescope for less money, "if you can handle the weight".
If you go the Mak route, consider a 200mm for better performance than a 6” apo. But again, acclimation will be a big issue so insulation or fans or some other acclimation strategy will be needed.
Another though would be a 130 F6 apo from APM with LZOS optics: shorter, lighter, easer to acclimate, great optics, better ergonomics than the 6” F8 and all that apo goodness.
That’s my experience anyway.
Below is a picture of the fans I had Deep Space Products add to my Mewlon 210.