What are the advantages and disadvantages of each and which one has proven to be the better choice?

There are HDI Chirp units. Get one of those and you can Chirp with 2D sonar and Tweet with your smart phone.

Raymarine has the Dragonfly units that Chirp 2D sonar and Chirp DownVision. Then you can have two Chirps and a Tweet.

I put a HDI transducer on my HDS Touch that is mounted at the bow.
I split the screen and have down scan and 2d sonar at the troll motor. That is what a HDI transducer will get you.
My unit does not have chirp. Have not seen a image on a chirp unit.
All I know is what I have read in tech articles.
Regular 2D sonar pings 1 200hz signal at a time.
Chirp sonar pings multiple signals ranging from 69-200hz at a time.
They say with a chirp unit there is a noticeable difference as far as noise and clutter.
But to get the full benefit out of a chirp unit you need a true chirp transducer. Lowrance chirps through a single frequency transducer which is not taking full advantage of the technology. Most purist are using a Airmar brand transducer that is compatible with Lowrance. About a $1000 transducer. Then they say that the chirp technology really shines when in water over 30ft. Much better target separation and resolution.
So as far as bass fishing I do not know if there is much of an advantage other than less noise and clutter.
Any Chirp owners out there?

From what I have read, I think you are correct. The CHIRP, when used with the traditional single signal transducer, is not nearly effective as an actual CHIRP transducer. From what I understand, the standard single signal transducer might be able to produce the low and middle CHIRP frequency, but not the high frequency. The high frequency is where the increased detail comes into play. This is just what I understand.

Ok, so it looks like I understood wrong. Here is a section from an article that I found that explains Lowrance CHIRP in the Elite units. I'm assuming it is the same with the HDS units. It seems that they are saying that the HDI transducer (83/200) will produce medium and high CHIRP signals and the traditional transducer (50/200) produces the low CHIRP signal.




Transducers comprise the second vital piece of the CHIRP system. Airmar Technology builds a wide array of options, from lower-priced transom-mount CHIRP products to wider-beam transducers and through-hull behemoths with 25 ceramic elements.

However, Raymarine has started building its own lower-priced CHIRP transducers, and Lowrance says that its SonarHub black box and new Elite-5 and Elite-7 CHIRP multifunction displays can transmit a sweep pattern through a traditional transducer, such as the company�s own 50/200 or 83/200 kHz Hybrid Dual Imaging transducers (which offer the traditional low/high transducer, and a 455/800 kHz imaging transducer in one).

�We�re getting two CHIRP ranges out of a single transducer,� says Lucas Steward, Simrad/Lowrance sonar product manager. �With the 83/200, you get medium CHIRP (with a 30-degree cone) for wide coverage and high chirp for awesome bait tracking. With 50/200, you get the lower range (50 kHz) for better depth.�

The main differences Airmar sees between using a CHIRP transducer and chirping on a conventional transducer are noise and range resolution, says Jennifer Matsis, Airmar�s vice president for sales and marketing. CHIRP transducers reject the flow of noise better, particularly as boat speed increases. They also separate targets more distinctly.

Traditional transducer signals also peak at 50 and 200 kHz. When a CHIRP signal transmits on either side of that peak (through a traditional transducer), the energy is mostly wasted, Matsis says.

�If you look at the formulas, that�s true,� Steward says. �The more bandwidth you have, the better it is supposed to look. But there�s an on-the-water aspect, and I have not been able � in most fishing situations � to see a huge difference.�

http://www.sportfishingmag.com/fishing-boats/making-sense-higher-and-lower-cost-chirp-sounders

This is starting to make more sense now. I worked in a crystal manufacturing plant while attending college to get my BSEE. Back then, we lapped in crystals to a set frequency depending on what the customer wanted.
You got a very pure, one frequency crystal and very little side frequencies.
That is why I could not understand how Lowrance (or anyone else) could transmit a band of signals from a single transducer. Reference the above article and Airmax has multiple crystals to produce the multiple frequencies. IF you want chirp (which is a band of frequencies transmitted at the same time) you need the multiple crystals. Otherwise you are really getting some software generated approximation of real chirp.
Maybe that is all we need for fishing? I don't know. But, I don't think you get real 'chirp'!

Agreed. You might get a more detailed image with the HDI transducer, but I think if you want REAL CHIRP, you'll have to drop the coin on a REAL CHIRP transducer.

When guys start running these new big screen Gen 3 units we will know more.
Some are going to run the high dollar chirp transducers and we will be reading articles in BASS and FLW about how its the new big thing.
I am curious about if there is really a big advantage in the 40 fow range. I am always a year or two behind the new technology.
Only way I can afford it.