I can't decide which one is better. Has anyone tried both of these and which one do you recommend? Thanks a lot.
That depends on if you want a 510 mod or a pod system, and how how a wattage you want to vape.
The 18 is a 510 threaded, dual battery, 230W mod. You can use any tank you want on it.
The P-5 is a single battery, 80W pod system which only fits the pod that is made for it. It much smaller in size than the 18 and is a different form-factor.