First, a correction: Instead of '2 locals' the DHG and S3 receive 2 subchannels from 1 local but can't receive the other one.
As someone who chases distant stations as a hobby, the DHG's tuner is OK, but not on par with today's tuners. It's sensitive enough for weak OTA signals - but it's Achilles heel is multipath. For example, I'm in between markets (Toronto & Buffalo). I keep my antenna pointed at Buffalo to get the weaker Buffalo stations. The closer Toronto market stations' signal strengths are still strong despite being pointed 120 degrees off course - but the DHG has trouble decoding them reliably. Meanwhile, latest generation tuners show 85-100% signal with no dropouts.
So yes, the DHG has a decent tuner, but most 2013 tuners will outdo the DHG when it comes to signals that are bouncing off of nearby hills & obstructions rather than direct line-of-sight (similar to the strong but multi-coloured ghosty signals you used to see in analog).
Please post examples of standalone 2013 tuners which exceed the S3 and DHG tuners. TiVo's Premiere OTA tuner is inferior to both earlier products, but of course it's no longer new.