I recently purchased my first bass boat and in need of electronics. I narrowed my search to Humminbird brand. In my price range I would like to stay at I can afford helix 7 di gps or helix 5 si gps. I would like some feedback on which one would be most benificial from people who have used these. 

Those units are like all the other units before them. The Helix series are just the current models. They do the same stuff the same way with the same stuff.

All my units are Side Imaging units and they do Side Imaging, Down Imaging, 2D sonar, and GPS/mapping.

I do not use Down Imaging for fishing and rarely for searching--only for demo screen shots.

Neither the Helix 5 series or the Helix 7 series are linkable to any unit with any connection to share anything. The Helix 7 has a faster processor and will handle mapping at speed better than the Helix 5 models.

IMHO, Side Imaging is a lot better than Down Imaging due to the coverage. Side Imaging shows from the water's surface to past vertical under the transducer on both sides. That is particularly important in shallow water where DI and 2D will only have about the boat width of bottom coverage. With SI you can have a couple hundred feet of bottom coverage at the same location.

As far as display size, I use the phrase "any Side Imaging is better than no Side Imaging".

Thanks that is helpful. I may wait longer and save to get the helix 7 si. I just like that size screen on helix 7 the best. 

Keep tabs on internet sales.  There have been quite a few of them lately where you can save a couple hundred dollars on these units.

There was a place that had the Helix9 si for about $750. They ran out tho.