I use Navionics on an Android tablet in BVI and its great. I've never run aground and I always point in the right direction.

iNavX is horrible, people. You have to know in advance which charts you need to look at.

MX Mariner for Android is steller. It automatically zooms you to the right chart and zoom-level for your GPS coordinates. It stitches the charts together automatically. Super clean experience and Free IIRC.

MX Mariner in the US + Navionics in BVI and Europe and you can't go wrong.

Also, I use the standard charts. And like I said, I've never had the charts do me wrong. We're talking line-of-sight navigation and piloting here.