Engadget posted a leaked photo of a Verizon Wireless marketing campaign that's being prepared to lure early iPad buyers into choosing Verizon over AT&T for 3G service. How so? Verizon offers the MiFi, a wireless router that connects to the Internet over Verizon's 3G network, and then allows up to five devices to piggyback over Wi-Fi.

The MiFi is a nifty device, fitting in a shirt pocket, working off a fully charged internal battery for four hours or indefinitely via an AC adapter.

The problem is the service plan. Verizon requires a two-year commitment from MiFi buyers for either a $39.99 per month plan for 250 MB of combined upstream and downstream usage (and 10 cents per MB above that), or $59.99 per month for 5 GB of combined usage (and 5 cents per MB for overages).

That's far more expensive than the 3G-enabled iPad, which requires no contract commitment, and offers two monthly plans: $14.99 for 250 MB usage per month and $29.99 for unlimited usage. There are no overage charges; instead, the iPad pops up alerts when the 250 MB limit is coming up and offers the user the option of upgrading to the unlimited plan for the rest of that month, a thoroughly rational approach.

Still, it's smart of Verizon to seize the opportunity to show alternatives. I've heard great things about the MiFi because of its flexibility and portability, and the way it gives users a single 3G data plan and hardware device that works with all Wi-Fi-capable laptops and handhelds.