File and directory structure differences between MT4 and 5

Hi to all. I have a couple of small customers to whom I give some stats from their servers, mainly derived from Apache logs. If they update to MT5, then I suspect that my scripts will have to change a bit. So, please pardon a broad and kind of vague question-- I just need to get a feel for what I might be in for. Regarding the file/directory structures of of MT, what are the differences between 4 and 5? For that matter, is there anything that shows up in the logs the give me (unfortunately, I don't have filesystem access) that would help me determine which one they're using? Again, a vague question... my apologies for that. I wish I could be more precise, but sometimes the vagaries of customer behavior make that difficult. Have a good day.