I'm not going to argue the case for mic versus pickup. We each have our preference. I've worked with both, and I know which I prefer (and it ain't a pickup!)
I am going to argue the case for having BOTH!
If you have a pickup and it fails, it's good to have an alternative. Same with a mic - if it breaks down it'd be good to have a pickup to fall back on.
If you use a guitar amp, then most pickups will need a preamp to sound good. Active pickups have a basic preamp built in (and need a battery), while passive pickups have no preamp. Most passive pickups sound weak and tinny, or just really harsh and piercing when plugged into most guitar amps unless you use a preamp. LR Baggs and Fishman make out board preamps that work well with passive pickups.
Both pickups and mics can give feedback problems when you crank up the volume. Best to experiment with your gear to learn the situations where this is likely to occur, and best to learn that
before you start going to play gigs!
I'd suggest getting a pickup
and a condenser mic and stand. Give yourself plenty of options, and the opportunity to learn what works and sounds best for you.
On Saturday I'm playing an outdoor mini festival. I'll be playing into a mic, but you can bet that I'll also have a stick-on pickup in my gear bag in case I need it!