This is bit like the question, "Which is better, blonds or brunettes?" Well, it depends, and the eye of the beholder is key to the answer.
I use a Lowrance 500 as a backup in my airplane - to be used when everytrhing else has quit. Never had occasion to use it except in training for the unthinkable. Nice unit for this purpose - just enough to get you pointed to the airport. But, with the small screen and limited features, I probably wouldnt elect to use this GPS as my primary means of navigation. At the other end of the range, when flying sparsely equipped aircraft, I use a Garmin GPSMAP 496. Larger color screen, approaches (limited) NEXRAD weather, etc, etc. Works well as the principal means of navigation.
BTW, since I assume that you are using the Lowrance for VFR operations, you can likley get by with relatively infrequent updates, say every 6 or 12 months. WIth this in mind, Lowrance offers a one time update service for $35 U.S. where they send you a new card in exchange for the old one, and no doohickey is needed.