If you buy a down scan,you only get down scan, you could have regrets. But if you get a side scan, you get the down scan you and won't have regrets with it.
Before I bought my HDS-8 I asked a lot of questions. Lots of guys (ifish being one of them) all gave the same advice. Get the biggest screen you can afford.
I think you already know the answer... get the big dog.