potassium permanganate vs potassium dichromate

simply heating can increase the reaction rate and the yield.
to compare, potassium permanganate is a stronger oxidizing agent than potassium dichromate (both are in aicdic medium). however, potassium permanganate is just too strong for oxidation of organic molecules. it may further oxidize the product formed (ie, ethanoic acid) into carbon dioxide and water, though it is not very common.
instead, milder oxidizing agents, such as potassium dichromate, are used. with similar reactions and reactivity, it will not produce carbon dioxide and water in oxidation reactions.

Sorry !
I think KMnO4 is a better oxidizing agent for ethanol to ethanoic acid.

Organic reaction is usually slow and low yield. KMnO4 is stronger and reaction goes faster. So, KMnO4 should be a better choice for ethanol to ethanoic acid.

When ethanol react with KMnO4, no matter under refulx or simple distillation, ethanoic acid will be produced.

When ethanol react with K2Cr2O7, ethanoic acid will be formed under refulx but ethanal will be produced when using simple distillation.