Because some limitations, this one premium is better than this other .
Both do the same thing just the premium will give more heat and energy cap and 5kg less in weight. Sure, because you have only 2, maybe will need one of the others. Now, for now only those 2 before trying to invest in the others between those two.
You need to understand that using those, will require normally some cooling and regen modules adding weight and losing room fast.
Modules that can be use and max controlled
Those are cooling and regen individual and energy-heat reserves with internal regen and cooling. You might need 3 of each one of heat and energy just to start or may be 3 for keep just 3 for now per mech. You will need 2 cooling and 2 regen per mech just in case of configurations need as counter base or help to increase limitations.
Max these two
Max 3 of this one if have or those 2 I can see. It is best in the sense of weight and functionality. Sure, the phys provide better HP but add weight. Been limited in weight unless playing as counter, is better use the heat one if not an energy mech so use the energy same type.
Good. Do not do the others and careful making too many if you are working just in 2 mechs. Preserve capital and mix boxes for primary and secondary mechs. Don't make too many for nothing.
You have some nice weapons around but focus on modules for a while. You will be fine with your inventory to some ranks, but modules are key to help your mechs.