I've got both a pump fed and a gravity fed drip system, but don't use either
It's a great option if you're growing all 1 strain and it's dialed in so you water the same amount to all plants, but wiht different plants uptaking different amounts it's hard to get it right without multiple res's and pumps.
I used the gravity system once and it worked awesome, but you need the height for the res. to get the pressure to work properly, if you can't get the res. 5ft off the ground at least it's not really an option. It works just as well as a pump fed system if you can get the elevation.
It's definitely an awesome way to go about things though, saves a LOT of time and knee strain. And is safer for the plants, I've snapped a few branches watering before. You can run shut offs on every line and monitor it while it waters and manually shut off the ones that are saturated, I've been debating this option for a while
I'm saving my systems till I find a clone I want to run a bunch of at once I think. With the number of plants you're running I'd definitely look into it. Really not that expensive either. Think I got all my hoses and fittings for $30-40. My res's were free. I think I spent more time/money on the fittings for the gravity fed system then I did on the entire pump fed.