It also depends on what you're going to put in there, and in what sort of soil.

These holes are generally good. For example a succulent/cactus and others which prefer good drainage would like them, as long as the soil mix was light and had good drainage.

Then again, if you're looking to grow tomatoes or something which might get really thirsty, you might actually consider drilling a hole(s) in the side of the pot an inch off the bottom or so. This is so that when you water it, you water until it comes out from the side hole, so theres always a bit of a "water reservoir" at the bottom.

But that won't do with plants which actually don't drink so much, as it'd just make it more likely for their roots to rot.

The technique as used in that form but by weed growers, is called "a hempy bucket", and you fill it with a light, well draining soil mix. Or no soil at all is pretty common (as in you still have a growing medium, but it's not soil, as in dirt) coconut husk/vermiculite mixed with perlite in about a 5050 ratio will make it "passive hydroponics".

Here's a guide. Don't worry even if it's for growing weed, the same applies to tomatoes, chilies and potatoes and whatnot harvest plants you might be growing on your balcony. https://www.rollitup.org/t/an-idiots-guide-to-hempy.386008/

But as I said, the bottom holes are fine. Just thought to share some info in case it's useful.

Edit forgot the link