Try the Serotta first. If you love it, keep it.
If you don't love it (it doesn't "disappear" under you after 100 or so cumulative miles) send it back. Call Bill, tell him what you did and didn't like about the Serotta. Tell him which of his suggestions appeals to you most, and why.
Let him help you decide which of the 3 saddles to try. Give it a good, long try. Like, 200 or so miles. A couple months. As the leather softens to you, the feel of the saddle changes RADICALLY. You have to give a Brooks a chance to show you what it can do. Be sure to use Proofhide.
If you have any issues, call Bill. He is a fountain of knowlege, and doesn't mind at all if you call him a lot. (I have called 3 or 4 times with questions about my B67.) Or post here, since there are a bazillion Brooks riders on TE. And with the 6 month exchange policy, you really can't go wrong.
I'm also 40, not going to race (but it might be fun), and most of my rides are 50 miles or less. I love my Brooks, and as it has softened I love it more. It "disappears" under me. I doubt I'll ever go for a different brand.
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson