Do both if it's a crit.

If it's a road race do the Cat 4. You'll probably have more company. Once you can hang a bit in the master's crits move to the master's road races.

When I was a 4 I'd do the 35+ 4/5, the 4's, and the 45+ on most crit days. Or at least 2 if I couldn't do 3.

How far are you from Houston BTW?