Few advantages with HDS units.
Faster screen draws/refresh, quick access keys to functions(8" and larger units), internal GPS attenna, units now will let you run any external model gps attenna(Nema 2000)from any vendor as long as nema 2000 (Great if your attenna fails you can use you friends Garmin),can add Lowrance new external GPS attenna GPS4000 series,built in Brodband Sounder (leaves open network port on unit so can cannect that to another unit and share sonar, older units use port to connect to Broadband sounder so you would need a network box expansion to share sonar), can add structure scan and other devices.
I won't upgrade as have 8" LCX37C with broadband sounder. I say go for it. Or you can save money and go for the 110/112 with a Broadband sounder and the cash you save, buy a good thru hull transducer. Transducers are the best investment and improvement to any sonar and most over looked. Most stock units supplied, work kinda OK and that is about it.
/fishon