i messed around with the gsp1101, Epsi and 11R tonight and came to some conclusions:

if you are used to a guitar rig in the room, the gsp1101 is more up your alley as easier to get that room tone without much eq.

by comparison; the gsp1101 cabs sounded closer to Ownhammer IR's without as much high cut eq.

i took an Ownhammer IR of a Scumback 75 (one of my favs) and loaded it into the gsp1101 and the Espi. i can hear a slight difference in the Epsi, but if i didn't have them side by side i would say the gsp1101's loader was perfect. it's hard to hear the difference in IR length. i can hear it more in the low end, which i roll off anyway. so the gsp1101 IR loader is pretty good.

i tried matching the tone of an Ownhammer IR with each unit using only stock cabs just to see which was easier:

i tried the gsp1101 using it's vintage 30 cab with a post eq BOOSTING high mids at about 4khz while cutting a little low mids at 560hz and it was pretty close.

the 11R with vintage 30 (4-12") using U87 off axis was the closest match, but much brighter and harsher than the gsp1101. adding an eq helped get it closer.

overall:

the gsp1101 stock cabs are warmer and closer to Ownhammer, but still benefited from a little eq boost.

the 11R stock cabs were brittle as hell by comparison and needed much high end roll off to get close. only a couple mic positions were acceptable (but still needed a little roll off).

amp model feel:

once the cabinet tone was right, they both provided plenty of good tone and feel. guitar volume roll off to clean was easy to achieve on each unit depending on which amp model chosen (marshall types were easier).

the gsp1101 DOES NOT model poweramp distortion at all. the amp level is nothing more than a volume control. the 11R rack DOES model poweramp distortion on par with the axe-fx II. so if power amp distortion makes a difference to you, the 11R is the clear winner. if you used a rack back in the day, then the gsp1101 is better than most everything we had back then. it's all preamp distortion, but so was everything in our racks. many of us never heard an amp fully cranked nor owned a power brake to safely turn our 100watt head full blast, so poweramp distortion wasn't a factor. i use it now, but i can't say it's the deal breaker.

something to consider......you could buy a gsp1101 used for a little more than the Epsi, and you would gain more amp models, effects and an IR loader, plus midi and the ability to change IR's with the presets. for me, it's a win. i can use it by itself or with the 11R.

it may be awhile before i consider doing a superpack for the gsp1101 though. you knows? if the demand was there i guess.

i will try to get some clips made this week. i will do some blind tests to see if anyone can identify which unit they are hearing. should be interesting.