Jolly or Adamant for Entei capture?

Question

I'm looking to go catch Entei in my save file of BD, but wasn't sure if the extra speed would be better.

Comments

What do you plan to use this Entei for?

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Nothing in specific right now. Just want to not have to worry about catching it later.

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It's sort of a personal preference, though I'm pretty sure most Entei run Jolly due to wanting as much speed as possible.

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Adamant is better

 Base 100 Speed is very fast compared to most of the Pokemon you're likely to face. Only in competitive battling are you likely to encounter faster, stronger threats to Entei where having that 10% speed boost may be important. In WiFi battling where tiers aren't so strictly enforced, you can't totally predict when the 10% speed boost is beneficial over the attack boost. Since most Pokemon are slower than Entei, it'd make mathematical sense to invest in attack to nab that KO than risk it. Of course there will be cases where your Jolly Entei is faster than their Adamant Garchomp, but you'd likely switch out than take your chances. I guess it boils down to what sort of opponents you face online, because in-game you're definitely faster (with EVs) than 99% of the opponents.

 Entei has access to Bulldoze and Extreme Speed, both of which can be used to make up for the speed differential, Scarf and Band sets notwithstanding.

Answer 1

I'd recommend getting a jolly Entei. A lot of Pokemon have 90, 95, or 100 base speed, and they can easily outspeed your Entei if it has adamant nature. According to Smogon, jolly is Entei's best nature in both UU and RU, so it's probably also good in wherever you're using your Entei.
source
Also if you catch Entei and later find out that it has the wrong nature, you can just use a mint on it.