Hi, definitely start with 2, it's overall a much better experience in all aspects and you don't need to know anything about 1 at all.
In more detail:
Sokobos 2 has more focused puzzles. Smaller levels, more about specific ideas and interactions, requires much less moves to finish a level. Better polish, animations and controls.
Sokobos 1 is more focused on larger levels that overwhelm you, with a lot of things in, often requiring too many specific steps to solve a level. It's more of an old school Sokoban design from the early days. Also no cart, sinking/floating objects nor water streams that move objects.