I also use a helix 5. The portable unit fits perfectly inside a bucket for protection while ice fishing and running miles by machine, runs for days off a small portable battery, and marks the exact same fish as any larger screened unit. You will want to put a mapping chip in it if you want detailed charts. The larger units are just that, larger. I have bigger units on my boat, and wouldn't go smaller, but for PORTABLE, i prefer the 5" screen.
S.