lacey, they are not the same and you would be nieve to think so, just take a peep inside at the cores.
Some companies use proper extruded tubes which are fully brazed to the header plates and finning,
some use extruded tubes which are glued to the fins and welded into the header plates, some use home made cores which have seam welded tubes with pushed in turbulators, also there are various different fin types, profiles on header tank design, bracetry etc.
The important thing to consider in all this, apart from the obvious performance issues is the strength of the cores-there are many 'bowed' coolers running around on cars- they are bowing simply because they are too weak- todays cossies are running higher and higher boost all the time.
ps.. why don't you use one of your coolers on your own car???