Well!
Really for
strength gains either one will certainly help you out, even though they work in different ways.
MassFX is formulated to raise free testosterone, while HFX has daa with the anti-estrogen 7-MF and forskoli.
For recomp most people will choose HFX over MassFX
But for strength and mass, MassFX tends to be recommended over HardFX since results are usually noticed more quickly. Size gains might not be as noticeable while on HFX being masked by fatloss.
Now as for TST, it'scontains daa and was created to work with either product and give that extra boost.
Possible Stacks with these three
MassFx+TST
HardFX+TST
MassFx+HardFX+TST
I've seen em all done by happy campers

Any of those stacks will help with strength, the rest is "how much" and "what else" do you want from your stack?
And aaaall that leads me back to, from what I've seen it would be best to try out MassFX solo first for the recommended 8 weeks. 2 in the morning 2 aprox 8hrs later. I know some of the guys have experimented a bit with dosages, like taking 2 of the daily 4 pre-workout, but they'll be in soon enough to share their tricks lol.
sorry if I rambled, I'm up waaay past my bedtime