This is dependent on if the game is modded, because in vanilla I would pick cyclops, but in modded I would pick seamoth. Cyclops makes a great mobile base, but it cant be enhanced with mods like the seamoth.
Always stayed away from the dunes cause I just thought it was a reaper-infested biome without nothing but heat vents. After I beat the game however, I came to love the dunes. There’s so much scrap metal and big nodes, and the reapers aren’t even that bad.