should i neuter him now or later?

i rescued a 5 month old cat, and i have 3 (adult) girls at my house. i did go to the vet and asked this, and she said it’s up to me. i don’t trust that vet a lot (she’s not the one who does the surgery, she only schedules it).

my question is, is it safer if i do it later, or there’s no difference?