I've used both the Lowrance and the Garmin products extensively for sounding/chart plotting. I'll share my experience and opinions on the pros/cons of each:
Lowrance Pros:
1/ Has more extensive database than Garmin wrt soundings/areas, but Garmin is slowly catching-up,
2/ Once you upload your sounding log (and pay a modest monthly subscription fee for Insight/Genesis) - you have much more ability to play with the data and produce much more informative maps than Garmin,
3/ Fairly user-friendly chart plotter/sounder as compared to Garmin
Lowrance Cons:
1/ Slightly more expensive than Garmin products,
2/ Doesn't update your contours in real-time like Garmin,
3/ Uploading your sonar logs requires larger mini-SDs and takes time.
4/ You can only record sonar logs and upload them with the newest versions of Lowrance products.
5/ It will only punch-out contours for your favorite harbours to download to your chartplotter using a restrictive export that requires your to identify each individual chartplotter
Garmin Pros:
1/ Decent hardware as pointed-out by other posters,
2/ Updates contours in real time.
Garmin Cons:
1/ Not as user-friendly as Lowrance wrt trying to figure-out options wrt sounder and transducer functions,
2/ The real-time contour revision requires very tight transect sounding tracks (like 50 feet or less) or it produces gaps and the contour plotting looks goofy and unrealistic unless you have really tight transects.
3/ You can't play with how wide your transect widths are and how realistic the contours are - unlike Lowrance/Genesis.
The transducers abilities are comparable between the 2 brands - if you can figure-out how to work your transducer and frequencies using the Garmin - which is more challenging, IMHO.
In short - if it is deeper and/or the areas you wish to map are larger - use a Lowarnce verses a Garmin product. That way you can change the widths on your transects (online using Insight Genesis and upload and download to your newer chartplotter) and produce more realistic contours w/o all the blank areas and clunky contours generated by the Garmin product.
