Ok, let's go over a few things.
The Panther and the Tiger were of course, heavier and better armed than most (MOST) allied tanks.
This does not make them superior by a large margin in combat. Tank versus Tank losses in the Normandy campaign averaged a 1.5-2/1 KDR in favour of the Germans, not that great considering the germans spent most of the time on the defensive anyways. In fact, post-normandy allied commissions found that allied tankers needed a 2.2/1 tank superiority over the Germans to be assured 100% success rates in combat, and Germans needed a 1.5/1 ratio to assure their own chances of 100% success. This means, in a wide gulf that included equal numbers, it was fair game for anyone (thus also helping to bust the idiotic myth that it "took 5 shermans to take out a tiger", which is utter bullshit, especially by operating under the hair-brained assumption that german tanks fought alone).
Now, you must also remember that the majority of German tanks in normandy were NOT Panthers or Tigers. They were the Panzer IV, which had a slightly superior gun to the sherman/cromwell's 75mm, and slightly heavier frontal armour. This meant that it's hull armour could deflect rounds from the allied 75mm and 76mm guns, but all the rest of it, including the frontal turret plate, was easily penetrable. In turn, the Panzer IV could knock out both Shermans and Cromwells at most ranges to the front, but was slower moving. So not all that much of a superiority, in fact rather balanced in terms of combat capability.
The real reason the Germans tended to win armour engagements with fewer tanks is that the German tank crew experience was much better than that of the allies, most of whom had never seen combat. This however began to wain towards the end of the campaign as the experienced German tankers were killed, and by September/October of 1944 in France, the German tankers were far more likely to suffer horrendous casulties against american and british tank forces (At Arracourt in September of 1944, a pure tank battle with German armoured superiority and surprise ended in a 3/1 KDR in favour of the americans).
If you have any questions about this stuff, feel free to ask.
But now, to the more crucial point, how will we represent this ingame?
Simple, it will be historically accurate. Allies will have access to greater numbers of tanks, but of course they will be historically presented with their generally weaker guns and armour compared to most German tanks. German tanks will be less numerous, but also historically presented. If tigers/panthers were used in a battle in any numbers, they will be in there, roaming around. Beyond that, it comes down to player competency. A good player in a sherman can easily defeat a good player in a Panther, all it takes is flanking without being spotted, or getting a lucky hit. Same goes for the Tiger. Just as well, a really good player in a panther/tiger/panzerIV/stug/whatever can dominate a map, but only if he is cautious and knows how to ambush and protect his flanks by working with other tankers.
Allies do, however, have trump cards. The british used the 17lber, a gun equal and superior, respectively, to the German 75mm L/70 (panther's gun) and 88mm. It was mounted both in tank destroyers like the Achilles, Shermans (the Sherman Firefly, which had a ratio of 1 per tank squad), and on it's own anti-tank gun mount. The british 6lber, when using sabot rounds, was perfectly capable of penetrating a Tiger's front with ease, and the Churchill tank, whilst still using the 75mm, had heavy armour that could deflect 88mm rounds. So the British will have tanks perfectly capable of taking on German tanks with advantage.
