I'm not sure why everyone seems to think that more power is always better. I agree being able to zoom at various levels is a nice advantage, but buying it because it has more power really shouldn't be that big of a deal. A Vexilar has all the power you would ever need. Even in deeper water it has no problems. There are a lot of times where you will need to turn the power way down on both a Vex and a Marcum to not pick up all the clutter in the water. With A Marcum you can only go so low with your gain. The Vexilar FL-18 has LP (Low Power) mode to reduce the power in these situations. This works especially well in weedy conditions as well. It helps filter out a lot of unwanted clutter. Personally I'm a Vexilar Man, and like the Three-Color Display differences of the Red, Orange, and Green compared to Marcums Red, Orange, and Yellow. The Orange and Yellow on a Marcum seems to blend together so there tough to distinguish the two colors. The Vexilar is just easier on my eyes, but that's my opinon.
It's going to come down to personal preference. I would suggest finding a couple people that have each unit and try fishing next to each of them and then make your decision on which one you like the best.
Now with Underwater Cameras I think hands down the Marcum 560 is the best that is out there right now. Using it in the boat proved it to be an awsome unit and I can't wait to see it in action this year through the ice.
Good luck!
LundMan