So, I assume your employer doesn't have a Roth option?
Higher expense ratio (.04 higher). [This can easily negate the 2 extra years of compounding especially once the chunk gets huge decades from now].
After 30 years, a .04% difference in expenses on a $6,000 initial deposit, assuming 8% nominal gains, is $667.25. Not earth-shattering. Meanwhile, two years of compounding (year 28 vs. year 30) is $8,613.30. Go for the compounding, particularly if you are thinking of the long-term. And, in my opinion, rethink the "benefit" of the ability to withdraw, for the same reason.
Now, if you meant a *4%* difference in expenses, that's crazy!