I own a fine SV125A ED OTA (AKA '5"'), f/7.75, one of the optically very good ones. I also own a Celestron 8" Edge HD (AKA "SCT") and a 14.5" f/4.3 Night Sky Dob with a fine John Hall mirror. I do most of my observing from my Bortle 6-7 backyard. For AP in particular, I drive 3-4 hr round trip to one of two Bortle 3-4 sites. Here are my comments.
First, re: mount, my AVX handles both the refractor and SCT just fine, both visually and during AP. I guess I got one of the good ones. Vibration is hardly noticeable visually, and shock absorbent pads are unnecessary. Given my light polluted skies, I really appreciate the "goto" feature of the mount and generally point it with a laptop running Starry Nights 8 Pro. The AVX is quite lightweight given the load it can support, and I simply carry the entire mount outside, then attach counterweights. The mount head fits in a Harbor Freight Apache 4800 Pelican clone case, which is great for remote sessions. This mount yields 1.2" rms guiding (both axes) using either the 5" or the SCT, which is better than the seeing at my backyard, and usually better than the seeing at the remote sites I use. I am thrilled with the AVX mount and have zero intention of upgrading. I just hope it lasts. For AP, I would add there are a number of "tricks," like loading the RA axis to the east, and slightly offsetting the polar axis to preload the Dec axis. It also helps to experiment with the PHD2 software settings to optimize pointing, which is a good thing to do during full moon periods.
The 5" refractor: great on double stars, and my "go to" planetary/lunar telescope when I don't think the seeing is quite up to snuff for the 14.5", which is 90% of the time. I think visually the refractor yields slightly better contrast on planets than the SCT. However, the SCT seems to outperform it slightly on the very high contrast Moon. Galaxies (all) are just plain disappointing from my backyard, however. Globulars may or may not be partially resolved but, again, the 14.5" Dob blows the refractor away. Some of the brighter open clusters, however, are quite nice in the 5". The 5" and SCT OTAs weigh almost exactly the same and I--a healthy adult in his mid-sixties--have zero problem mounting either scope onto the AVX with legs fully extended. I think it is important to be a bit **** retentive when carrying/handling the 5" because it doesn't have a handle. I built the observing chair with a height-adjustable seat as described in the first edition of Phil Harrington's book "Starware." This is especially helpful when observing near zenith as the seat can be adjusted low--the "swing" is much greater than for the SCT, something that might be worse with a 6", depending upon one's f/ratio and lens weighting.
In comparison, the 8" SCT is slightly easier to mount than the 5" due to its shorter tube and convenient handle. Eyepiece "swing" about the sky is much reduced, too. DSOs are of course considerably brighter in the SCT, to the point where it even begins to get fun to locate galaxies from the backyard on transparent and Moon-free nights. I use 2" eyepieces with my SCT so the ~ 1.25 deg field (30mm ES 82 deg AFOV) isn't too bad, although the refractor clearly has the wider field. This only seems satisfying at dark sites, however, because the lit gray background of a wide field simply swamps fainter DSOs. The SCT will resolve the cores of the brighter globulars--M5, M13, and M22 for example. Needless to say, the 14.5" yields much brighter views of DSOs.
The 5" refractor is easier to setup and use for AP. I use an Evoguide 50mm guidescope with this OTA, and it locks on like a Gila monster. There is a bit of flexure, and dithering is your friend. I use a Celestron OAG with the SCT, however, and I sometimes must hunt for guide stars even at f/7. The COAG is also more sensitive to star SNR (see my post on this). That said, I use both often and like 'em both!
'Couple of things about using these telescopes visually. For a given magnification, the 5" has a smaller exit pupil than the 8" and a much smaller exit pupil than the 14.5". For those of us oldsters with floaters, a small exit pupil (~<0.7 mm) can be begin to be a problem. Then too, for a given magnification, the 14.5" yields a much brighter image, hence promoting better contrast detection, than either the 5" or SCT.
Both the SCT and the 5" refractor "live" in quality cloth cases, and both are easy to transport to a remote site. The 14.5" must be disassembled into box/truss/base, etc. and is a real monster to transport to a dark site. Night Sky telescopes are quite wonderful but they are not at all light, following as they do more or less the design philosophy of Star Master scopes. However, the 14.5" has wheelbarrow handles and thus is the quickest scope to set up in my backyard. Like other posters here, I seem to require ~ half a dozen trips to/from the garage to fully setup with either the 5" or the SCT. Neither the 5" refractor nor the SCT is "grab and go," and I am certain a 6" refractor on an equatorial mount would not be either.
So there 'ya have it! Honestly though, I kinda wonder about keeping three telescopes into my dotage. If I were limited to two, I'd keep the Dob and the 5". If allowed only a single scope, I'd keep the 8" SCT.
Happy observing always,