Was Voyager really significantly slower than the Enterprise?

In the Next Generation episode "Where No One Has Gone Before" the Enterprise is catapulted to another galaxy, roughly 2.7 million light years away. From that location Data says it will take just over 52 years for a subspace message to reach Starfleet, and LaForge calculated it would take over 300 years for the Enterprise to return at maximum speed.

LAFORGE: Well, sir, according to these calculations, we've not only left our own galaxy, but passed through two others, ending up on the far side of Triangulum. The galaxy known as M Thirty Three.

PICARD: That's not possible. Data, what distance have we traveled?

DATA: Two million seven hundred thousand light years.

PICARD: I can't accept that.

DATA: You must, sir. Our comparisons show it to be completely accurate.

LAFORGE: And I calculate that at maximum warp, sir it would take over three hundred years to get home.

[...]

LAFORGE: Message on this has been transmitted to Starfleet, sir.

DATA: Which, traveling subspace, they should receive in fifty-one years, ten months, nine weeks, sixteen days

PICARD: Mister Data!

_{emphasis mine}

Data's odd notation of time not withstanding, that breaks down to about 52,000 light years per year for the subspace message and 7,700 light years per year for the Enterprise (presumably not accounting for refueling, repairing or exploration).

Now from Voyager's premier, "The Caretaker", Kim states that Voyager is over 70,000 light years from their previous location, and Janeway says that at maximum speeds it would take over 75 years to return to Federation space.

KIM: Captain, if these sensors are working, we're over seventy thousand light years from where we were. We're on the other side of the galaxy.

[...]

JANEWAY: We're alone in an uncharted part of the galaxy. We have already made some friends here, and some enemies. We have no idea of the dangers we're going to face, but one thing is clear. Both crews are going to have to work together if we're to survive. That's why Commander Chakotay and I have agreed that this should be one crew. A Starfleet crew. And as the only Starfleet vessel assigned to the Delta Quadrant, we'll continue to follow our directive to seek out new worlds and explore space. But our primary goal is clear. Even at maximum speeds, it would take seventy five years to reach the Federation, but I'm not willing to settle for that. There's another entity like the Caretaker out there somewhere who has the ability to get us there a lot faster. We'll be looking for her, and we'll be looking for wormholes, spatial rifts, or new technologies to help us. Somewhere along this journey, we'll find a way back. Mister Paris, set a course for home.

_{emphasis mine}

Using these values Voyager can travel between 900 and 1000 light years per year at maximum speeds (again assuming no considerations for maintenance or exploration).

These numbers suggest a large disparity between the capabilities of the Enterprise and Voyager. Had the Enterprise been sent to the Delta Quadrant they presumably could have been home in about 10 years, not to mention that they could have messaged Starfleet and had their message received in about 15 months.

Was Voyager really that much slower than the Enterprise?