I suggest you go to BPS/Cabelas or any other store that has a good selection of FF's so you can actually see 'em, punch some buttons, change the view on the screens, compare the different brands & models to see which one you prefer. Ask the clerks some ?'s as well. Fish with some one who has a model(s) you like or interested if all possible. The larger the screen the better when considering down scan or side scan, you need the largest screen you cannot afford :shock: for the detail these functions can provide.
The HB 859 has lots of good comments as do most HB's. A buddy has a HB 899 si I think, seems like a good unit but he uses the 2d for the most part. He also has a Low Elite 5 with down scan & gps, but does not use it much. I've played with both of these and the pictures are good so it depends on the screen size you're looking for and how you plan on using the FF.
I can say the base mapping on HB or Low is good for getting you to the area you want to fish, marking waypoints for structure, etc., but do not show the detail you are probably looking for. If you want the map to show the greatest amount of detail, you will need to get one of the aftermarket cards for your area. Navionics may have more detail for your area while Lakemaster stinks, or vice versa. Check with you local buddies or google those products and find out if others are happy/satisfied with their choice. I like the Lowrance/Insight mapping, it has sufficient detail for my style of fishing while others do not and want more detail, so they purchased map cards for their lakes.