I own a 302. I have had zero problems with it.

No 303. Instead of the 303 I use a PDA to give me moving map,
navigation, other soaring task information, thermal analysis, etc.

Some pilots use a PDA plus a flight computer's navigation display (like
the 303) so that they can be analyze two possible turn points at the
same time. They do this to help make real time decisions during
contests. That is an advantage of the SN10 as it also provides an
additional navigation display. Personally I have enough on my hands
watching one display.

The other thing to think about is cost. The Cambridge system is less
expensive.

- John