I'd say no for the Sazabi simply because of the price. Yes, the old HGUC is a bit dated but its also not going to cost you nearly as much, plus from my own personal experience you might actually be able to swap the weapons, whereas my RG Saz had the wrist peg snap simply trying to remove the damn thing. Plus, there's aesthetics - as the name implies, Real Grade is designed to look real, so you have segmented plates, opening parts, etc. but that may not necessarily be what people want. Between the HGUC and the RG, the HGUC one still looks more like the one actually in Char's Counter Attack. Likewise for the old PG - it's not as nearly complex, but if you aren't going to display all the opening hatches or want it looking that realistic, the old one is likely a slightly cheaper option. A better example would be Char's Zaku II because that glorious bastard has two variants within two semi-different lines, that being HGUC and Origin, though with Origin it really is just the same kit with different stickers (compared to how there are two Char's Zaku I kits that actually ARE physically different in minor ways, mainly color). The original HGUC Char's Zaku II is one of the earliest offerings and is extremely dated compared to the recent Revive which has an entire rubber skirt option purely for leg clearance in certain poses, namely all the kicking Char does (to the point this is literally the box art). In this case, unless you want the vintage experience of the true original HGUC kit, there's absolutely no reason for getting the first kit as there's nothing it offers the Revive doesn't do a zillion times better. Similar cases would be the Blue Destiny Gundams, since they just offer so much more like options on Unit 1 for manga or game head details. By the same token - and indeed, the same model as the Blue Destiny units - the old Ground Gundam isn't as nice as the newer one, but if you don't need all the fancy new tricks the newer one does, the old one is still perfectly serviceable with a little work.