If mechanical issues were the only consideration, studs would be better than bolts. The clamping force of the nut pulls the threads of the stud against the Al without any rotational friction which is why wear doesn't occur with a stud. Also, more accurate torque values can be obtained because there is only the stretch of the stud plus the friction of the nut against the washer, whereas with a bolt there is also the friction of the threads against the Al.
However, the convenience of being able to (rarely) remove the rocker box without removing the head is an additional consideration. Although bolts do cause wear of the Al, remember that primary covers are removed and replaced much more frequently than a rocker box ever will be and the resulting wear on those Al threads typically isn't an issue.
As far as I can tell from reading what seem to be authoritative sources in books and manuals
, studs only should be finger tight in the head. "Preloading" the studs in the Al, which many people commonly do by "double-nutting" them during assembly, does nothing to help. Given this, if the studs are installed finger tight they should be easy to remove even if in the course of tightening the nut the studs rotate slightly to jam them somewhat tighter into the Al. However, the amount of protrusion of the studs above the rocker box might require making a pair of thin "jam nuts" for their removal. While cutting slots to allow removal with a screwdriver instead of double nuts would work, it strikes me as a pretty crude thing to do to a Gold Star engine.
Anyway, it seems to me that either replacing the studs with cap screws, or installing the studs finger tight so they can be easily removed, are equally good solutions to the problem of removing the rocker box without disturbing the head. If I ever have to remove the rocker boxes from my Gold Stars I have to hope the rebuilder (me, in one case) was aware of the 'finger-tight' rule.