I like SPI for the flexibility, but also it just opens up new strategies. If I'm not SPI, for instance, I don't find nationhood, CS, or pacificism to be reasonable civics outside of golden ages (and of course you don't want to be drafting in a golden age, so I never use nationhood if I'm not spiritual). But with spiritual, I can use 5 turns of nationhood/theocracy, draft myself into the ground, then switchout with a load of rifles while my cities wear off the draft-weariness. Or, doa 5 turn run of representation, CS, and pacifism if I need a great person or two 
. and there are a lot more little things like that (switching religions on for temporary gain) that just aren't feasible for non-spiritual civs - the rules of the game are just completely different .
FIN & SPI are really the only two civs that have benefits in early, mid, and late game. Neither have the quick early boost of EXP and CRE, but those two just aren't that useful anymore 100 turns into the game. imo.
are you picking last?
. and there are a lot more little things like that (switching religions on for temporary gain) that just aren't feasible for non-spiritual civs - the rules of the game are just completely different .FIN & SPI are really the only two civs that have benefits in early, mid, and late game. Neither have the quick early boost of EXP and CRE, but those two just aren't that useful anymore 100 turns into the game. imo.
are you picking last?
Please don't go. The drones need you. They look up to you.