I use mostly plain base and have no application where I am even trying to go faster than just a little over 2000 fps.
Some boolits intended for use with gas checks shoot fine without. Some on the other hand seem to be more accurate with the check. My 7 TCU is definitely more accurate with the check installed on my Lee 128, but I think this may be more of the bullet staying better aligned in the case neck at my desired COAL.
The one application where I see a gas check as strongly recommended is for gas guns like the AR-15. In 300 BO guns and in a 357 Max AR, I had lead deposits in the bolt area when shooting without gas checks. This tells me that the base of the bullet was being gas cut as the base travels over the port. These applications also seem to have more than typical flyers. Again I attribute this to the same bullet base damage described above.