I guess it all comes down to budget; but, yeah, you know the old saying, “Buy once, cry once!” TDS meters are cheap but getting an accurate pH meter isn’t cheap. They’re not stupid expensive but they’re not cheap either. You can always pH your water with the drops kit. I just find it difficult to determine color with some additives (like Recharge) that produce a very dark colored solution. For most things, though, you can just use the liquid drops test - they’re very cheap. The pen is just much more convenient.
Hope this helps - happy growing!