I'm in the SAL Taca lounge as I write this. Very easy airport to transfer through. Lounge is as described above, with free booze and WiFi. I have transferred through both MGA and TGU without having to go through customs. MGA will require a escort through security/carry-on bag scanner back into terminal. You cannot follow the sheeple exiting the airplane in either, you will have to tell the agents/officials that you are transferring, and maybe wait to be escorted back to the secure airside in both.
If you have never landed in TGU, I would choose that for the experience. There is a lounge there, but I think it is only for Credomatic Credit Card holders like San Pedro Sula. You can try with the Amex Plat, but YLMV.