I wouldn't see any need for a front end Pre if you already have a 702. Those built in Pre-Amps are amazing as they are!

The MP-1 is a fantastic little pre though, and I can see how it would improve the R-44 sound.

I use four Sound Devices mp-1s in front of an Edirol R-44 and I really like it. I set the mic pres once and then fine tune on the Edirol as needed.

I've just gotten a SD Mixpre-D in front of my Sony M10. Put it together for SFX & ambience recording, though I haven't used it extensively, so far seems like a great portable combination for me.

The biggest pro is the ability to record with proper mics. You can't go wrong with a SD pre-amp.

The con is me feeling like developing it to a full sound kit with more gear (i.e wireless sets).

I know that michael raphael uses a cooper mixer in front of his SD recorder for the pres.

My view is that if you have a handheld and are using the internal mics, then a mixer front end runs counter to the portability/size/weight/stealth/ease form factor of those things.

If you're using external mics and stands, then having a proper front end seems like the appropriate thing to do regardless of your recorder.

with the 702 specifically, I'd only feel a need for a diff front end if I wanted more monitoring and routing capabilities in the field.