The most important feature on a depth finder is the vertical pixel count. As you probably know Vertical Pixels is the number of little “dots” that make up one column of a fish finders display. The more pixels you have – the more detailed the picture will be. I always suggest that walleye anglers have at least 200 VP’s – more is better. Another important feature is grayline. Grayline helps you distinguish different sizes of fish as well as “bumps” on the bottom. “Bumps” are often walleyes and are displayed as a widening of the black line that indicates the bottom. “Bumps” are good – I often fish “bumps” and catch lots of walleye. As far as 1500 watts compared to 3000, there are two places more power seem to make a difference. Deep water (over 30 feet), especially if you are looking for thermoclines. Thermoclines on a powerful unit show up as a line of clutter – the unit is actually showing the change in water density between warm and cold water. The other place I find power important is in mucky basins where the walleyes are belly to the bottom. Both of the units you mention have great pixel count, both units have grayline. Look at your fishing conditions to determine whether or not the extra power is needed.
Good Walleye Fishing