Yeah I think I spite of the grade 2 boost being obviously helpful, since it provided both a speed and strength boost... I mean, if Goku could turn into grade 2, he'd easily overwhelm the Cell who fought him (if Cell didn't power up more ofc)... The manga wasn't clear on that. Goku stated that all in all, the regular SSJ was best --- and that now he knows it --- and as such, he and Gohan should work on making that their natural state getting rid of that agitation, that restlessness... Making it a casual state, that didn't make them like if they took a few energy drink bottles. Though since that would still be insufficient since the grade 2 offering a power up on top of SSJ would still obviously help, I think the route of training as MSSJs, making it their natural states, offered them a bigger power up over the long term than going the buffed SSJ states, and that mastering the SSJ wouldn't allow them to assess the grade 2 power any longer. Not that the MSSJ was a multiplier = or > grade 2, but that the bugger power up as a result of this regimen training would kind of take their SSJ to the limits without it necessarily being a higher boost than 50x, just that the SSJ rate increase when training under SSJ constantly took it to its limit in a power gain way while not needing --- and being unable to as a valid and profitable exchange --- to go buff states.
I think as a consequence Vegeta and Trunks went the same training route of mastering the SSJs as they didn't use the grade 2 states in the CGs. While Goku and Gohan kept SSJ transformed throughout the time, I think it's likely Vegeta didn't want to showcase going under the same training route and Trunks, who knows, maybe he just got the mastery over it and didn't need to be as SSJ constantly much like the adult SSJs didn't need to in the Boo arc. Vegeta and Trunks' aura seemed to remember that of a MSSJ as well in the Cell Games if I'm remembering right, so I think they benefit from the power gains such route allows them, though still, since they had already overstrained their body before, not allowing enough room to recover and going full obsessed, their gains in it were still limited. Plus, Goku seems to extract most of his trainings anyways as per Vegeta in the Boo saga stating Goku's a greater genius and that even though he (Vegeta) would work harder, Goku had a special way to maximize his training.