I'm buying a used pontoon boat tonight (YES!), and an anchor is not included...

I've searching around, and I found a few kinds of styles:
  1. One is a pyramid, in 5 or 12 lbs. (sold at Cabelas, made/distributed by Outcast, I believe)
  2. A fix tined anchor (looks sort like a cylinder sea mine)... not sure weights... seen these on drift boats a lot.
  3. a normal style anchor with folding tines (I have one of these for my kayak). The one I have is 3 lbs.

I'm not sure which to buy. I'll mostly be using this in rivers, probably not to anchor in some really raging water, so I would think the 12 pound pyramid one should be more than enough to hold me... but really I don't know. the 12lb pyramid one is $60... and that is just expensive enough that I'd rather search out opinions before buying.

I'm about 170, and the boat is a dave scadden skykomish sunrise (10.5 feet long).

Thanks for any suggestions/help.