I know that almost every one of us use wine or vinegar for marinades or meals. Recently I was cooking a Chinese food and tried whisky instead just for a difference. That bitterness of the whisky tasted good in my opinion. What are the downs of this compared to a wine or vinegar?
The main factors a base liquid can contribute to a marinade are:
You did not provide a recipe, but in most Chinese dishes, the vinegar or rice wine in the marinade contributes some acidity (rice vinegar not always being as strong as western vinegar), possibly some sweetness, and of course, the characteristic flavor. However, Chinese marinades are not normally used for long enough periods, nor are they acidic enough for the acid to be an active ingredient; it is just part of the overall flavor balance.
Therefore, whiskey should serve well for most purposes, assuming you like the flavor it brings. While it probably has less acid than vinegar or wine, this is unlikely to be a significant difference.
There's no downs if you are using it as a flavoring and it adds the effect you are looking for, except maybe cost. Good whisky is very expensive compared to wine or vinegar.
Wine and vinegar are acidic, and acids can be used for tenderizing meats as well as adding flavor. Whisky is only mildly acidic, so it's not a good choice if you want to tenderize, if there's a downside it's that.