Wayne P ....., you are not giving us any help
We understand the differences ,,,,, we know the older units are on close out prices
We also understand what the units have / have not
What we are asking ..... without someone answering .... what ever we think about whether it is worth the $$$$
Is Mega a good improvement
Is Mega "worth" additional $$$$
Is CHIRP a good improvement
More like ..... is a blinker trim switch worth it ?
You can still make the motor go up and down with the switch on the throttle lever, but the blinker trim switch is nice
A better question might be ....... HOW MUCH is Chirp and Mega worth
For the waters I fish <40, Humminbird CHIRP has no value---excluding the new Dual Spectrum DI transducer. I don't see any difference using it or not. Recorded fish look exactly the same. Examples at the end of this post.
As far as the MEGA frequency, it is very good for detail but has limited, range, coverage and depth capability. What I do is use 455 kHz for searching since it covers from the water's surface to past vertical on both sides and has more range. THEN if I want a sharper image of a subject, I re-scan it using 1200 kHz to get more detail.
Sort of like using 455 kHz and 800 kHz to do the same---just a little better.
If you are like a lot of others that don't take the time to fully learn how to use your equipment and take advantage of what they can do, you will gain nothing with the extra cost except a lighter wallet.
This is the same fish, same day, almost the same time using dual beam 83/200 kHz and its CHIRP range to show arches.
THEN if you want Humminbird's best CHIRP 2D, you can get a Helix MEGA DI unit
or change the SI or Sonar transducer with a SOLIX to the MEGA DI transducer and have a Low-Q 2D single frequency range of 140-240 kHz. If you don't know about Low-Q, do a web search for it. A current model is the ONLY way to have that feature=$$$$$
THAT is "worth it" for better target separation.