me personally i can get by with mostly standards but i require a few deeps for particular applications. really for 1/4" and 3/8" drive it doesn't cost too much to get both at the same time and that's what i did there, but for 1/2" drive where it is pricier and i had to break up my buys into chunks, this is what i did: first, i got a socket set with ratchet, BB, extension and like 14 SAE standards right off the bat. second, added a T-handle and 14 metric standards and this gave me a good base 1/2" set that i've been using so far (anything that needs a deep in what i routinely do, can be done in 1/4" or 3/8" drive). now that i've got that base, i'm adding 1/2" deeps as i can find them inexpensively; i'm starting with SAE deeps just because that's what i found a good deal on and later on i will fill in metrics. this worked for me, i never at any point was like, "man, i should have got deeps first".
in a way this question comes up more on the higher end of the socket market where sets of deeps will often cost 50-100% more than standards once you get into larger drive sizes 1/2" and above. these HF sets cost the same so price falls out, i guess it all depends on your application; if you work on a lot of stuff where it is confined clearance maybe you want to get standards because you will have a lot of places where you put a deep on and then the ratchet doesn't fit. if you are working on stuff where you have lots of room to work and stack up stuff on a ratchet, sure, deeps will do everything a standard socket can do and more.