I have the Helix 7 SI combo. So far the only CON is that the mapping software isn't great (not detailed, no contour lines). But it does take the Lakemaster or Navionics chip I just haven't gotten on yet. Other than that it's seems to be a fine unit. Never used the Lowrance so I can't comment.
"Life is a matter of luck and the odds of success are in no way enhanced by extreme caution." - Erich Topp, German U-boat Commander, 1943.
When in doubt, set the hook.