Actually tails does mean more chakra.
The point that the eight tails was trying to make was that more chakra doesn't always mean stronger.
Take for instance genin Naruto and Itachi. Naruto has tons more chakra than Itachibut at that point Itachi could have killed him rather easily. That is what they were trying to say with that, because a person can have individual strengths without having a ton of chakra.
But anyone can see that the more tails you have the more chakra you have. It is indicated by the fact that everytime Naruto gets another tail in his tailed beast cloak, he grows more powerful and has access to more chakra. Everything points to this, and with what I said above it makes perfect sense.
Also you have to remember that Akatsuki was trying to save sealing the 9-tails into the Gedo Mazo statue for last because it had so much chakra that if it was sealed before the other 8, it would throw off the balance of it all. So clearly the 9-tails has enough to equal the other 8 bijuu.
At least the whole 9-tails, I would guess that the 9-tails with half it's chakra could definitely equal 5 tailed beasts considering that they are 5 of the weaker tailed beasts (chakra wise).
So yeah it actually makes perfect sense.