Just something I came up with while watching "In a Mirror Darkly", from the series Star Trek: Enterprise.
I tried to match screencaps with the mentioned warp factors, but I could be off a bit.
And before anybody comes with different warp tables between TOS and TNG, it took Enterprise about twelve hours at Warp 8.4 to cross a thousand light years.
Voyager would have needed 75 years at maximum warp for 70,000 light years.
Do the math, and tell me which one's faster.