Where would the real disadvantage be...

[Lysimachos]

When Hitler invaded them the Polish tried a cavalry charge at his tanks.

That is a popular myth: The Polish indeed used cavalry (as did germany, russia, romania and others, too!), but they were used for scouting etc. In fact there are no reports on an occurence where cavalry was engaging tanks, though it is still a popular story.

[Strategos Alexandros]

Really? I didn't know that.

[Ludens]

According to Wikipedia it is actually a Nazi and later Russian propaganda myth. However, the article goes on to claim that Polish cavalry did on one occasion charge elements of a German Panzer division, and drove them back. Off course, for all we know these "elements" might be scouts or supporting elements, not tanks. It also worth bearing in mind that most German tanks at this stage were of the Pz I or Pz II type, which were little more than armoured cars.

[Strategos Alexandros]

That might have been what I was thinking of.
(Although I could just have been being stupid)

[russia almighty]

Ludens I could have sworn the story was, that the Polish cavalry had cut down a decent sized unit of Germans and got ambushed by those said panzers.

[Watchman]

Like all of their kind, the Polish cavalry of the day was basically mounted infantry - being able to range far and wide independently of roads and the logistical "tail" of fuel supply, such mobile troops had an obvious usefulness in the wide open lands of Eastern and Central Europe (the Finnish army had a cavalry corps too, incidentally; presumably chiefly because while horses aren't all that hot in forests, they're still way better than motor vehicles there and in any case were much more readily available). AFAIK they did however mount the occasional succesful "cold arms" charge on suitably exposed German troops - infantry caught on the move in the open being the most obviously vulnerable one, but it's not like the open-topped halftracks and whatnots weren't potential victims too. Soviet cavalry is known to have occasionally mounted charges in the grand old form as well, with varying degrees of success (generally contingent on how well they were "shot in"), and German medics every now and then had to treat sabre wounds inflicted by cavalrymen harassing stragglers and retreating troops.

Random trivia: whatever their reputation for mechanised warfare, a good 90+% of WW2 German troops nevertheless either had to leg it or relied on horses for transport. The first ones to field genuinely mechanised armies were the British (a lot of the Germans' horses were actually surplus British stock that had been replaced by motor transport, bought before the outbreak of hostilities) and Americans - and even they used vast numbers of draft animals on the logistical side.

[Aper]

According to
Warfare
a site usually very reliable, the polish cavalry attacked german infantrymen in 16 occasions, and in almost all the polish won. Too bad the site is only in italian...