Thunder vs Thunderbolt

Thunder is better due to one hard hit.
For defense thunderbolt will be better

At higher levels, Jolteon is strong enough to take a charged Twister so I definitely prefer Thunder which will decimate like half of Gyarados health...

Makes the battle seem less work overall to me...

Ideally, 2 Gyarados are in a row since usually the first is near death when you can fire off another Thunder.

Both are effective and comes down to preference. I like one bar charge moves, so prefer Thunder.

Thunder is better overall. If I know I am up against hydropump, I prefer thunderbolt so I don't lose out on energy waiting to dodge.
The same holds for other 1 bar v. 2 bar options.

I think higher damage one bar charge moves are better when I am attacking by myself. But I think quicker two bar charge moves provide better flexibility and less wasted energy when I am attacking with another player.

Its thunder. slightly better, but both work well.

Why is giving everyone just some advises without any reference to the simple numbers? Thunderbolt has pretty much exactly the same DPS. Assuming you will use exactly 100 Energy with the one, that has TBolt, then the T one has dealt exactly the same damage in the same time, with the difference, that the energybar is going to be filled up a little more. Thunder is a full bar move, so its gonna take a few cycles though to get off an additional Thunder and I think Jolteon wont survive long enough to ever make this come true. So in fact, it simply doesnt matter! I'd rather be more energy efficient to take out a Gyarados just before the Dragonpulse starts, that you would have eaten with Thunder and be flexible in terms of dodging.
Thus, I highly recommend you Thunderbolt!

Thunder for Kamikaze attacks, Thunderbolt for dodging.

If I'm attacking Twister Gyrados I prefer Thunder, for Dragon Pulse I prefer Thunderbolt. HP Thunder.