The kids were fiddling with a two cam music band shoot and one camera was set to 4:3 and the other 16:9. Both tapes are now captured in PP1.5. They know they can scale up and down in Premiere. Which is the preferred method? To scale the 16:9 to 4:3 or the 4:3 to 16:9???

Is there an alternative method to match the cameras?

They now know to synch and double check the cameras but they still need to make this project work.

Any advice woiuld be greatly appreciated.

Actually, regardless of whether you do a 4:3 project or 16:9 project the other footage would have to be scaled up. The only way you could avoid this would be to do a fake 16:9 project. I.e., do a 4:3 project but mask it to appear 16:9. Then you would just have to scale down the 16:9 footage to fit the 16:9 bars.

This is all assuming, of course, that the 16:9 recorded on the one camera is true 16:9 and not the 16:9 created by the aforementioned masking effect. Some camcorders record 16:9 by this method.

The cams were both Panasonic DVC30. One was set to letterbox / 16:9

Scale both to the intermediate 14:9? i.e. lose the sides of the 16:9 and the top and bottom of the 4:3 - but: not much from either!

The cams were both Panasonic DVC30. One was set to letterbox / 16:9
If it is letterboxed (aka fake 16:9) and not true anamorphic 16:9, then you can still do a 4:3 project masked to simulate 16:9. You just won't have to scale down the letterboxed "16:9" camcorder footage, since it is already "pre-masked."