Your Best Distance?

I need these. 

I think I'm going to run a 5k this weekend.  Well....one on July 2nd that is a super informal race.  I want to do it mostly because it's on Saturday.  

There are a bunch of kick-a looking 5ks in Southern California on Monday, the 4th of July, but I want to run Saturday for these reasons:  

1) Group bike ride on Sunday will make me sore for a Monday race and I don't want to miss it!  

2) I don't want to stress all weekend about running a 5k.  I want to have the option to overdose on diet coke and Say Yes To The Dress on Sunday night.  Hopefully while enjoying the glory of my PR!  

3) I want to set a benchmark ASAP to work off of

4) If I really want to run another one, I'll just run two in a weekend!  

Yay America!   

Am I overthinking this?  

Yeah.  For sure.   Why?  

Because 5ks scare the bajeezus outa me.  

They are fast, painful, and reminiscent of high school cross country racing frustration.  And I don't think I'm very good at them and I don't do them often.  My adult PR is a 21:18 and I know I can do better. I've always felt like I'm best at the half or full marathon....if there's one thing I'm good at, it's plowing through long sustained uncomfortable situations (both in running and in life), and I think that translates.

 However, the Runners World Race Predictor Calculator doesn't seem to think so.  

For a long time, I've thoughts that these race predictor calculators are kind of wacky.  When I typed in my 5k PR, it predicted two times on the distance extremes that I think are off the wall:

Best Mile:  6:24

Best Marathon:  3:23:55

uhhhhhh really?  Please find me a 3:23 marathoner who can't run a 6:24 mile while hopping backwards on one foot in their sleep.  

I don't mean to knock a perfectly free service, but why does it seem so inaccurate?  I tried another race calculator that more closely predicts my times, but still is a bit off and predicts a faster marathon off this fairly mediocre 5k I ran on little training in early 2010.  

So I wanted to get your thoughts on two things:  

1) What do you think your 'best distance" is?  

2) Have you had the same confusion with the race predictor calculators?  Are they BS or am I just complaining too much?  :) 

PS:  Everyone who entered the Bachelorette giveaway is a genius!  Almost everyone still has their top 3 in the running !!

(On another note, when I read this post again, I worry that it sounds egotistical or overly race time obsessive. My apologies if I'm coming off this way...)