It really comes down to what sort of use you expect that you'd get out of both. As it's been mentioned the weight capacity and abilty to put bigger loads on is an advantage if that's what you plan to do.
Really the Polarie is strictly dslr based although there has been people using a Lunt 35 with a DMK with success and I'd wager it would similarly handle a PST and possibly small guide scopes for widefield.
Personally I feel the AT and Losmandy are better suited for comparison and the Polarie is more of a stand alone product for dslr's.
Pricewise I think the Polarie wins out again, the Starlapse would set me back 800 Euro minus the tripod.
The Pentax would require a new camera, itself costing lets say 470 Euro(less second hand) for a cheaper Kr plus another 240 euro for the astro tracer. This again is minus tripod and lenses/adaptors for the Pentax.
The Polarie cost just 429 euro, no tripod. And can be used with no polar scope if needed.
I'd honestly just buy the unit and source a different tripod to the kit one or you may already have an acceptable tripod.
Personally(and I am biased) I'd go for the Polarie it wins or is equal too in all departments apart from load capacity.
Sorry for talking Euros by the way, just it's what I paid so what I use for comparison.
