I want to set up my new 7 g tank and looking for the best base substrate between seachem and tetra. What do you guys think the best base substrate between 'em ?

Seachem and tetra are brands, which type of product are you talking about?

Usually you only need one complete substrate.

Seachem and tetra only market substrate additive in Indonesia and not the substrate itself.

Seachem with the flourish tabs/starter pack.
Tetra selling initial sticks.

You need to add gravel to both.

Another alternative is to use JBL aquabasis/florapol or sera base fertiliser.
Sometimes you can also find dennerle.

So far a complete enriched substrate existing in the market is only Azoo plant bed. Look for then at ACE or Malaliwe LFSs. It looks a bit like ADA soil.