I would check the fees in the transamerica plan.
Is the TR fund 0.18% there? Sometimes the same fund will be more or even LESS expensive in a 401k plan. So check.
Also see what fees the 401k plan has, any admin fees. I would just call and ask.
What is the expense ratio? Are there any maintenance fees? Are there any management or 12b1 fees not already included in the expense ratio? Statement fees, annual fees, etc?
If the total is greater than 0.18% look at the IRA and consider the differences between a 401k & IRA already mentioned.