The Eeveelution that you start with has been an interesting topic in the XD community. Some pros and cons of both.

Espeon pros:

Espeon's special attack is slightly better than Jolteon's, leading to more OHKO's and less damage rolls in some cases.

The rare unprotected Earthquake is less fatal, though Espeon's physical defense is still absolute crap.

Cons

Any dark type will have to be dealt with by Ursaring, losing time in some cases.

Since Bite is much less powerful than STAB Thunder, unless Ursaring gets a crit with Double Edge, you're losing time in the fight against Lugia.

Jolteon pros

Thunder is more powerful than Psychic, and can sweep through most bosses in the game.

Jolteon gets Thunder much earlier than when Espeon gets Psychic.

Jolteon has a higher speed stat, so a quiet nature won't hurt as much.

Cons

Loses time in Naps, Snattle, and Gorigan due to the electric typing of Thunder.

Thunder has 70% accuracy compared to Psychic's 100%. So you either have to be the luckiest person alive, or buy a crapload of X Accuraccies.

Unprotected earthquakes will most likely OHKO Jolteon.

What do you guys think about Jolteon vs Espeon?

I've set a 5:01 using Jolteon so I guess to put my perspective here. Please note that my route was very bad, didn't get double-edge, and didn't make use of EXP. Share optimally.

1. You have to do an extra battle to get the TM for Thunderbolt as you can't learn it by leveling up. It's a small detour but that alone will cost a few minutes unless you wanna YOLO the rest of the cipher key lair and citadark with a 70% accurate move.

2. It has slower animations, Bite is like a second slower being used by Jolteon compared to be using by Espeon.

3. Hidden Power would make this a very interesting choice to come back to since HP Thunder 70 prior to snattle would help a lot.

Aside from these couple points, I have no idea if Jolteon could ever overtake an Espeon run, the extra speed doesn't help it as much, and there's so many fights where enemies have ground types or the Lightning rod ability.

I'd say in a perfect run with perfect rng it's so hard to determine who's better but unless someone returns to do runs with Jolteon that threatens the top times, Espeon will be the new norm. Don't let that deter you from trying, however, as this game still has a long way to go before we're at that point!

I usually run with Espeon, but I do find Jolteon routes to be interesting. It's like Typholsion/Suicune routes in Colosseum. Doesn't save time in a lot of situations, but it's fun to theorize.

In the case of Suicune, it actually saves and loses time, but you need perfect luck when catching it.

Getting back to XD, XD speedrunning has been going on for about 6 years, and we're still learning new stuff. Unless there is some form of consistent RNG manipulation a la Heartgold/Soulsilver, you can almost never get perfect luck. Pokemon and RPG speedrunning is revolved around RNG so much that there should be some manipulation involved.

There is a form of RNG manipulation for Colosseum and XD, but unlike Heartgold/Soulsilver, it's inconsistent.

Hopefully, I can finally record a run when I have the time. Optimal exp share use, double edge, hopefully above average stats for both starters, and Espeon at level 11, optimally.

I usually run 2D Sonic games and Majora's Mask, but Colosseum and XD, mainly XD, are interesting to me because they're underdeveloped, movement optimization is really hard due to the 3D space, and it's more based on movement, luck, and routing. It's not like Sonic 2, for example, where the run is based on abusing physics and frame optimization. It's fun.