The main differences IMO between the VX5 and the VX7 are that the VX7 is newer, it is submersible and it is made to transmit on the 1.25 meter ham band as well as 6m, 2m and 70cm out of the box.
Very few ham radios transmit outside of the ham bands without some sort of modification, whether it be holding down 5 buttons at once and turning on the power button, or actually snipping some wires or pulling diodes inside of it, the VX5 and VX7 incliuded. While these radios will receive out of the ham bands out of the box, they will not transmit outside of them without the modification posted earlier.
I'd prefer a VX7 over cheaper radios for the fact that it can receive the VHF-low band, where the output of many drive-thru's are. Many HT's can do 2 meters and 70cm and be modified to go between 138-174 and 400-500 MHz, but not so many can hear between 30-54. This can be accomplisehd with any old scanner, but if you're looking for an all in one solution, the VX7 is it. Also, it receives AM broadcast, shortwave, FM broadcast, cordless phones at both 49 (where it will also transmit) and 900MHz, VHF/UHF TV audio and most other services up to 999MHz. The sensitivity does vary greatly and the antenna that comes with it is only made to work optimally for 6, 2, 1.25 and 70cm. It will transmit just fine on FRS, GMRS, MURS, drive-thru's, wireless mics at Sea World, whatever. The only thing you could do better would be a W32A or D7 since they can receive and transmit at the same time, but I don't think they have 6m capability, their battery life stinks and they're priced $100 more, although crossband repeating a neighboring McDonalds into a Taco Bell drive through could be interesting.
The VX7 can also scan for PL tones being used and DCS although I've never heard of a drive through using DCS. I've heard a McDonalds one using a rapid touch tone at the beginning of their transmission, 0 for speaker and # for headset to headset, combined with a PL tone. A lot of drive thru's are now going to 900MHz ISM band, which are unlicensed, or licensed in blocks but either way they don't appear in the FCC database. These are wideband FM which can be received by the VX7 but it cannot transmit there, not that the VX7 can transmit a wideband FM signal anyways. If you were close enough and had enough power, you could transmit at half the input frequency thus creating a harmonic at the input frequency, but it still would be narrowband and the voice would sound very quiet. You could probably modify a Motorola Maxtrac or similar to operate at that frequency and bandwidth. Drive-thru's using this system can be identified by the headsets without a belt pack and have buttons on the side of the headphones. 3M makes them, HME may now as well. You can pull up the detailed specs on their website for any of their headsets or any of their things including their Opticom traffic light changer for emergency vehicles, thanks 3M!