should i contribute to Roth of increase TSP contributions

I an 63/f. Started working at the PO later in life. Currently have a little over $200,000 in TSP. Was going to increase my contribution to 20% from 15%, but was wondering if I should start to contribute to Roth instead of increasing TSP contribution. I'm not where I wanted to be in TSP at this point, but supported my kids and parents on my own, so couldn't contribute as much as I wanted to earlier on. Trying to make as much as I can before I go. As an FYI.... my current contributions are 70/20/10-C/S/I