Here's something to consider, even though it doesn't take into consideration the actual strength of either Chidori or the spinning move. The spinning move obviously takes alot of concentration and practice to master, and is basically all about controlling chakra flow - something that Naruto usually has alot of trouble with. But if he can control his chakra well enough to get this move down, then you have to think, what does that mean for his abilities overall? Naruto isn't just learning a new technique here, he's also going through another training (like the tree climbing and the water walking). That means better chakra control, and with the amount of chakra Naruto has, and increase in his control makes a big difference in his strength.