Shoot the APX 100 you have. Why take a loss on it? There's nothing wrong with this film.
As for which to use afterward, you can start experimenting anytime. Try some of each. See which you like better.
If you spend too much time chasing the magic bullet you'll not spend any time shooting. Besides, who is to say that someone else's "magical" is yours?
Pick one film. Shoot it. Develop it. Tinker with different developers if you like (on noncritical subjects). See what you like. If you find something that really works for you, take baby steps out from that point. For example, when I discovered how nice Tri-X in PMK was I started trying Plus-X, FP-4 and HP-5, since they are broadly similar films chemically. These experiments bore a lot of fruit for me.
I tend to experiment to excess myself, but I have core products that I use consistently. Everything else is experimentation for fun, and very occasionally I discover something that rocks my world a bit. That's great, but find those epiphanies somewhat organically. Don't force them.