However for PE8 V's 80lb JB. They both test at 100lb. JB is thinner
Also I haven't heard of any shock load issues with the JB like some PE lines.
Inevitably, that depends on the nature of the test. I would prefer to use the manufacturer's stated poundage (for reputable manufacturers like these two at least). On that basis, for JB Solid 80lb the Varivas Avani GT Max equivalent is PE7.
Line thicknesses are very important to me when GT fishing - the lighter the better relative to the shock load and straight line breaking capabilities.
I do by the way, really like JB solid... just not quite as much as I like GT Max. If you take price into account though, choosing JB makes a lot of sense.
And as you say, unlike certain other big profile Spectra lines, it does not have a rep of exploding under shock.