I can't speak to Lowrance as I've never used one. The last time I fished, before I retired, a basic fish finder was the latest technology and I had a hard time reading it, so I'm new to this tech. I decided to take fishing up again after I retired.
I started with a Hummingbird Helix. The model I had did not have networking, so it was not compatible with forward looking sonar like Megalive 2. It did have down imaging which was easier for me to read than regular sonar and higher resolution, but after doing some research, I decided I wanted to try the forward facing imaging. That is why I upgraded to the Xplore.
It was a big learning curve getting all the tech to work, but once I got it working, it has been great. The Xplore has regular sonar, down and side imaging built in. Through the network, it can also use the Megalive 2 sensor.
Just from a quick google, it appears the Eagle Eye 9 is sort of an entry-level all in one unit. It does have forward facing sonar, but has a narrow beam angle and less capable sensor than the higher end system. It is significantly less expensive since it is an all-in-one system.
I'm not sure how it compares in resolution to the Megalive 2. Before I bought mine, I went on line and watched a lot of videos. They gave me confidence that I would be able to identify different types of structure and such before I purchased it. You might want to do that with the Eagle Eye and see if you like it.
At least with the Humminbird, there were a bunch of instructional videos on youtube. Guys would go out and record there sonar and then come back home and put the Xplore 9 in playback mode. They would then talk about how to read it and what you were actually seeing. There were videos for down imaging, side imaging, and forward facing. I found these very helpful.
I'm still only using a fraction of the capability of this tech, but I'm catching more fish than ever before. I think there are a couple reasons. First, the only structure I could really identify in the past was structure along the shoreline that I could see with my eye. Second, even if I could identify a piece of structure under water with regular sonar, there was no way to mark it and go back to that spot. With todays tech, I can actually mark a waypoint when viewing the sonar image. I can touch the screen on the structure. The Xplore figures out where that structure is relative to where the boat is now and does not mark the current boat position but marks the actual structure. Now that I have the Terrova electric motor, I can tell it to go to that waypoint I marked and spot-lock right over the structure if I want. Third, with Megalive 2, I waste much fewer casts. You can't see fish that are tight to the bottom, but can easily see any that are suspended. I don't only cast to fish I see, I often cast to structure, but I know there are fish within casting distance.
I will say that actually watching fish react to your bait has been kind of iffy for me. I was able to pick up the larger crappy jigs I was using during the summer some of the time. I have not been able to use the smaller jigs I'm using in shallow water this spring. However, I seem to be able to pick up larger bass lures quite easily. So I'd say a lot depends on the lure you are using.
Hope this helps.