Sicilian Svechnikov or Modern Defence? Which is more strategic?

The Sicilian is against e4, and Modern Defence is against d4?

If you begin with 1.g3 or 1..g6 you are giving the other player the choice on how to define the game and the central pawn structure. So at this point you need to know potentially what to do against nearly all openings that can be transposed into. Likely against 1.e4 you will get the Pirc opening but not a guarentee. You may even end up in a hyper accelerated dragon. You will have a wider variety of games. If you play the Sicilian you may not always end up in the opening variation you desire due to move order issues. Playing strategicaly is how you decide on your use of the materials in the game you play as this is your plan which means you have general deployment goals and objectives to meet during the game. The technical aspect is order of operations and tactical choice to obtain strategic objectives. That can be done in any opening and is usually best if you have a strategy for each opening you are likely to meet and the ability to formulate a new one if the position goes against expectations.

what do you mean by more strategic?

The dirty harry Sicilian with 2 Nc6 3. Nf6 4 h5

Simon, is that you?

Sveshnikov > Modern Defence objectively
There is a reason why Sveshnikov is played at top level, even in world championship matches and Modern Defence is not.
At your level it does not matter.