Thundershock does 5 damage in 0.6 sec. Raw DPS 8.33. Including STAB, DPS 10
Volt Switch does 20 damage in 2.3 sec. Raw DPS 8.70. Including STAB, DPS 10.43
Both are electric type moves, so if one gets STAB, the other also definitely gets STAB on the same Pokemon.
However the true DPSes on Jolteon's and Raikou's pages contradict each other:
Jolteon: Volt Switch (12.17) > Thundershock (11.67)
Raikou: Thundershock (13.33) > Volt Switch (12.61)
Also, how does Raikou's 9 extra attack stat, 3.88% better than Jolteon's, make its Thundershock 14% better than Jolteon's?
The damage equation adds +1 to each attack, so that even very weak attackers inflict at least 1 damage. This has stronger proportional benefit for weak attacks. The True DPS on the pages is calculated assuming that the defending Pokemon has 100 defense. Depending on the exact numbers of the attacker stats, for very similar values he might be just above or below an integer value, in which case flooring will make a large difference.
See the damage mechanics page for details.
