I guess I need to put my 2 cents in this discussion. As far as HB vs. Lowrance, I purchased a 787c and a 797c Si 18 months ago and had trouble with the screens looking like acid rain. I called the customer service line and they said to box them up and they would fix them at no cost. Since it was in the middle of tournament season , they put a rush on them and I had them back in 7 days. Pretty good service. Now here is the real reason I would buy HB. With the new updates available for the 797, I carried it in for the upgrade and it got zapped. The factory sent me a new 798c 2i and it works great. It also has a card slot for taking pictures on a reading card for later looking. As far as the external or internal, I like the internal because when you mark a spot, you are on top of it and holes were drilled.