Acorn Sprint vs Bierman Sprint

I'm in my first year of tri's, and have completed the NJ sprint tri in July (91 minutes), and will be doing the Nation's tri in September.  I've come a long way off the couch to 5k since January, as well as doing my first tri and losing 60 pounds so far this year.  To cap off the year before turning 50, I'd like to do one more tri in October.  My choices are the Acorn Sprint, or the Bierman Sprint.  I like Acorn because it's flat and warm lake temperatures.  I like Bierman because it's closer to Bethesda, and a little longer distance, similar to an Olympic, but a little scared of the hills.  I'm still riding on an old '86 Raleigh Technium 480  (52/40 chainring), so it's a little heavy for the hills.

Any thoughts on my final tri this inagural year?