There is no direct cross reference between those two models. 

Autel does have a functionality list per model. So query the database and compare the results. You can find it here:

https://pro.auteltech.com/measurecarApp-1-1.html?m=94&proTypeCode=MK808TS&operatorType=2

BTW: I used to have a MK808. I found out that the next step up, the DS808, has some additional functions compared to the MK808. It has the exact same functions as the MK906. I sold the MK808 and bought a DS808.