The A129 Duo is probably the best overall for a 2-channel cam. Avoid the "Pro" version as it's got a list of unresolved issues. Always research your choices before buying- there's an A129 Duo forum here
Vantrue has good build quality, and decent vid performance but customer service is marginal and updates are lousy. The N4 is an underperformer because of processor limits. I'd stay with 2-channel cams till the next generation of processors arrives and even then caution will be in order till they're proven.