I've owned both phones. The E72 for about a month in April. And the E5 for the last 5 days. Both phones a have their good points and bad points.
For me the camera is the deal breaker for me on both phones. On the E72, the optical trackpad made it difficult to focus and activate the shutter. (yes I know it can be disabled, but then the it makes navigating through everything else more difficult) On the E5, the camera is standard fixed focus, instead of Nokia's enhanced fixed focus. Pictures tend to come out somewhat fuzzy, instead of having crisp. Makes it impossible to take pictures of anything other than landscape, in perfect lighting.
The screen is the biggest difference, I would recommend the E72 over the E5. For one, the E5 washes out when used outdoors. But, the E5's screen can also be hard to view at an angle.
They both share the same processor, but the E5 has 256mb of RAM and 250mb or onboard storage. The E72 only has 128mb or RAM and the same storage. The E5 seems to run a little smoother than the E72, even with transition effects turned on. I don't feel there is a huge difference in the speed of webpages loading. But that may be due to network speeds.
They E72 has a larger battery (1500mAh) than the E5 (1200 mAh). Even with the same processor, the E5 claims to give 25% more battery life than the E72. I can't confirm this yet, since I haven't had my E5 long enough. I do recall being able to get almost 3 days from my E72.
In my opinion the keyboards are pretty much the same. I actually like the menu key layout on the E5. The E72 seemed to be a little cramped.
The battery cover on the E72 can be a problem for some. It would fall off too easily. So, what does Nokia do? They made the the cover on the E5 too difficult to remove.
After owning the E5, I may actually go back to the E72. I've gotten used to using just the Dpad on the E5. Or I may just wait to see how the E7 performs. Either way, I don't see owning the E5 into December.