My answer: Goku
I don’t feel that base form Vegeta is quite as strong as base form Goku (who is said to be in the realm of a Super Saiyan 2). So even if they both received the x4000 at the same time in the Baby Saga it stands to reason that Goku would STILL be the more powerful Saiyan.
Now you are probably arguing that SS4 Goku and Vegeta were equal since they were able to fuse with ease; without them taking a moment to align their Ki like they did in Fusion Reborn. That is true BUT you have to remember a number of factors that not only confirms Goku being more powerful but explains why it seemed that he and Vegeta were more or less equal to each other while fighting against Omega Shenron.
1. Goku had more experience as a Super Saiyan 4 because he reached it before Vegeta.
True, he never mastered the form so we never really see the extent of a SS4’s TRUE power if the user mastered the form but understandably he would probably have a better grasp over the form than Vegeta
2. Goku doesn’t have a “time limit” or “energy restraint” like Vegeta has as a Super Saiyan 4.
Remember that because his tail wasn’t re-grown but rather force grown by the Blutz Wave Generator, Vegeta could only maintain the SS4 form as long as his body still had the Blutz Waves that he was blasted with coursing through his body so technically SS4 Vegeta is similar to a SS3 in terms of him only being able to maintain the transformation for a limited amount of time due to his body not being able to handle the strain of the form for long because his body runs out of energy/Blutz Waves the longer he is in the form; wow Vegeta never reached SS3 but SS4 takes the same toll on him as a SS3 would!
Remember since Goku was able to re-grow his tail without the use of a machine, his power in SS4 Goku only runs out (in terms of him no longer being able to handle the form and growing weaker) if his source of Blutz Waves is cut off completely. In GT that would be the Tuffle Planet acting in place of the moon similarly to how he grew weaker as a SS4 when Baby-Bulma used the machine to focus all the Blutz Waves off of the Earth (acting as a moon) to Baby making him stronger and Goku weaker.
That being said, it can be assumed that Goku can maintain the SS4 form longer than Vegeta. Since Vegeta reverted back to base form when his body just ran out of Blutz Waves while fighting Omega Shenron and yes Goku was the first to revert back to base form but he had been fighting in the SS4 for much longer than Vegeta and that leads to the next point.
3. The reason Goku and Vegeta were more or less even when fusing and then battling Omega Shenron was only because Goku was weakened greatly because as Trunks pointed out, he had been fighting much longer than Vegeta.
Before the fight with Nuova Shenron he was literally running on fumes because he was hungry and was on the run before his Ki finally came back and he was able to transform into SS4 again. He took damage from that fight as well as when Eis stepped onto the field, he was blinded “cutting his power in half” (kind of like Gohan against Cell after his arm got damaged) BUT Goku proved him wrong because even without sight his other senses were increased.
Then he was brutally beaten by Syn Shenron so badly that he reverted to base form.
It wasn’t until his sons and Trunks restored his power was he able to surpass his limits making him even MORE powerful as a Super Saiyan 4.
He was able to overpower Syn but after he became Omega Shenron he took A LOT of damage and lost a lot of Ki especially in that x10 Dragon Fist Kamehameha Wave.
Now when Vegeta made the scene (well even before that, Bulma commented that he had been training like never before meaning that he was now more powerful that he was in the Baby Saga, most likely due to him being once again being motivated to training in order to obtain SS4 like Goku did), he was fresh from not fighting and then transformed to SS4 and seemed to be Goku’s equal.
If I had to guess, I’d say that SS4 Vegeta was equal to SS4 Goku (Baby Saga) just remember that Goku had fought the likes of Super 17 and 6 other Shadow Dragons by that time so now factor in with “Saiyans get stronger after every battle” into the formula and it’s easy to see why Goku would still be more powerful than Vegeta.
Not to mention he had surpassed his limits! So, Vegeta made the gap between he and Goku’s power smaller but the gap was still there.
Seriously, if Goku and Vegeta were both at 100% and fought each other at SS4 before Goku headed off with Shenron, I have no doubt that Goku would win!
If there was one thing that could possibly make all of my above talk false it would be this ONE statement made by Vegeta after de-fusing from Goku when their Fusion time ran out; “Look at you, you aren’t even worth my time!”
He was referring to Syn Shenron who had lost the other 6 Dragonballs after being hit with the Big Bang Kamehameha. Now it is difficult to say if SS4 Vegeta could defeat Syn Shenron if he was undamaged like he was when he first appeared. The only reason that he was beaten before was when Goku risked his life absorbing more power than his body could withstand in order to surpass his limits to outclass the one star dragon. Remember Syn was badly injured by Gogeta’s attack.
So, if Goku or Vegeta had attacked him before he started absorbing the Dragonballs again it stands to reason that either one of them could destroy him for 2 reasons;
- He didn’t have the 5-star Dragonball meaning that he would not be able to “regenerate” with the Electric Slime like he did after blowing up from the Super Dragon Fist
- He was badly damaged from the Big Bang Kamehameha so his power level was probably way lower than it was when he was able to easily overpower Super Saiyan 4 Goku (before he surpassed his limits)
If Vegeta was capable of defeating Syn when he was at 100% that would mean that Vegeta WOULD be even with Goku after he surpassed his limits in order to defeat Syn.
However, I’m more inclined to think that Goku would still be the more powerful Super Saiyan 4.
What do you think?