HI Tim A trash pump usually will have an open impeller, This means that it is designed to have an intake of a certain size foreign object without it damaging the impeller. Although not advertised this causes a bit of inefficiency on the hi pressure side a closed impeller is one where the impeller has all tight tolerances in reference to the housing and no slots in the impeller to allow easy passage of foreign objects. Commercial open impellers usually will state the size of a lone stone that it will accommodate. A quality pump will last no matter what type it is as long as it is used within it's tolerances.

The 2 big differences between a trash and a centrifugal pump
As Walter says, a trash pump will allow a certain amount of small 'trash' (rocks, sticks, sand, twigs) to pass through without damaging the impellor or internals
Some trash pumps don't use impellors, if they do it's a very loose tolerance
Where as a centrifugal pump has a very tight tolerance. The impellor to the pump housing, and will not tolerate trash being put through it
Impellor damage is not a good thing

The other difference is pressure
A trash pump can not and will not create the pressure a jet log (suction jet) utilizes to create a vacuume to lift material up the suction hose
Not to be confused with a suction nozzle that most highbankers use that pushes material through the hose
In most cases a trash pump can run a suction nozzle but not a jet. Jet requires a much higher pressure a trash pump cannot produce
In my opinion, a centrifugal pump will last longer if taken care of, no trash, no sand, nuttin but clear water
On the down side they cost more as a package
If you are only running a highbanker, go trash
If you are considering a dredge with a jet, centrifugal pump

Hope this helps

Bill

Good advice gentlemen, as I will be using it to run the highbanker, but want to be able to dredge with the highbanker also I think I will pay the dollars upfront for a centrifugal pump, 2 inch should be enough for my purposes. I am looking at the Gold Hog Piglet.

Tim,
I run a 2" clear water pump that I bought at harbor freight and it works great on both my highbanker and my 2 1/2 inch dredge with no problems, and in both clear and muddy water. As long as you take care of it they will last. I have had mine for over a year with no problems and also have a 1" from there as well that I have had for over 3 years and it still runs like new.

Tim,

A 2" discharge will be way more than is needed
Which is a good thing, you can throttle back and still have enough pressure

I believe the 4"dredge I had had an 1 1/2" discharge and was able to throttle back

Bill