There are many variables involved in choosing which you feel is best. For instance, you got a Helix 9 instead of getting the Helix 10 or 12 which have more pixels and better quality picture. Then there's the new Mega units which make units like your 9 pale in comparison. You say your friend gets great pictures. What unit is he using? If you don't get one with the same or similar specs then you would not be seeing what he sees, quality wise.
Then there is the settings on each unit. If you do not have the knowledge on how to set yours up for optimal viewing quality, it will never show what another 9 might show on the screen. I have used humminbird si from the 898 up to the 1st gen Helix 12. As I got newer and better equipment the picture has looked better but having an electronics guide who truly knows what he is doing, set up the unit and show you how to read what you are seeing, you may never be happy with your unit regardless of the brand. My HB si units were lacking on the DI views IMO because of the blended DI. I recently put a HB DI unit on the bow and now I have good DI views. I have not had the opportunity to see what the mega DI looks like in person.
Like most things, you get better quality with higher priced units so since you are on a budget in the purchase, expect that you aren't going to get the best views possible but look for one that you can live with. I would suggest that you buy whatever unit you want but then pay the couple hundred that it will cost you and go see someone like Slade out at Fork and have him tune them for you and teach you. It is money well spent.