GTA V's Los Santos compared to GTA 6's Vice City. Worlds apart: different real-world references, different design philosophies, different decades.
Reference cities
Los Santos = Los Angeles. Vice City = Miami. Both actual places; both heavily exaggerated in-game.
LA's coding: film industry, traffic, sprawl, valley-vs-coast geography. Miami's coding: beach tourism, art deco, Latin flavour, intracoastal geography. Distinct energies.
Scale
LS in GTA V is famously south-heavy, with density thinning out to the north. Based on trailer footage, Vice City looks like it will be dense from end to end, with the suburbs carrying that density into the inland transition.
Combined, Vice City + Leonida is plausibly bigger than LS + Blaine. Vice City by itself vs LS by itself would be closer.
Architecture and feel
LS = modern American glass + Vinewood Hills mansions + Vespucci beach + industrial waterfront. Vice City = art deco strip + Brickell-esque downtown + Star Island mansions + port. A different visual vocabulary.
Density
Vice City looks denser at street level. We talk about it here: the density vs size piece.