i have been looking at a lot of Gunpla lately and have seen some 1/60 models that are not PG. but they seem to say Real Detail. they are much cheaper than PG which says to me less detail.
What it really means is less internal
detail. Depending on the kit it may be a similar level of external detail (some PGs, especially the older ones, I guess, are very light on external detail.) I think non-grade big-scale kits can be great when they are priced reasonably
. Like 4000 yen for the 1:60 Strike, or 4500 yen for the 1:60 Exia. These kits are simplistic (in terms of construction) compared to a PG or even a MG, but a good value if what you want is a large, detailed display piece for not a huge cost.
Ultimately you have to make up your own mind how you feel about the different versions. Personally I'd break it down like this:
1: Most likely, just save your money and get the MG instead.
2: If you really want a big-scale version, go with the non-grade only if you understand and accept the limitations. It's essentially a giant "High Grade" but with nicer detailing.
3: In general I've often come to the conclusion that it's worth paying more for the better kit. Choosing which one is the "better kit" is often subjective of course... But pretty often the better kit really is the one with the higher price.