But what I would add to all these very good posts is the following, no matter how many hatches you have the actual fact your Tank has been hit will motivate you in getting out PDQ, however, lady luck will always decide what happens to the crew, you either get out or you don't, if say you are in a Cromwell & get hit by a Jagd Tiger I would put your chances of escaping as slim, due purely from the kinetic force the impact will impart of the Tank, the shock of such a hit would be devastating to say the least. But again this all comes down to where you get hit, what the round hits or goes through as it enters the Tanks internal space, and also if it enters and does not just hit and bounce off the armour or just sticks in the armour. clearly in the example I have given the chances of a 'bounce' are very small and not amount of 'Training' would save you from that fate.
Historically a classic example would be Wittmann, Total 'K' Kill on 007 his Tiger on the 8th August 44, good crew, very experienced and no one come out, and extreme case maybe, but it does I think highlight the point, easy access in and out of the Panzer, but the hit was so powerful they all went pretty much in one hit/brew up.
'Buck' Kite from my old mob 3 RTR is another example, a very good TC, MC with 3 bars IIRC and he was hit going over the crest line of hill 112, he told the crew they were going to be hit as he was ordered to advance by Major Bill Close who was being pressed by the CO of 3 RTR to 'get on' (really nice bloke, dead now but a nice man to talk to), they got ready for the 'Hit' and as Buck predicted within 30 meters of clearing the crest line they were hit, 3 of the crew managed to get out if my memory serves right, two of the crew did not, all who got out were very badly burnt. Now this was from a crew who knew or at least were pretty sure they were going to get hit and more than likely had all hatches open (4 on the Sherman Kite commanded) and so would of been waiting for it as it were, but still 2 died and the other 3 were hurt badly, lady luck strikes again.
Another example is Maj Bill Close himself, on the 18th July first day of Op Goodwood he told us on a battlefield tour of the Goodwood fight in 1991 that he had 4 Sherman's shot from under him that day! sod that for a laugh, he lost some of his crews but they kept on getting back on another Sherman and cracked on, Legend!
all the best
Perry