Both will work for you, each has their own set of pro's and con's.
Pullright - heavy, not an issue for your 3500, but what options do you have for lifting it out when you need the bed of your truck? More expensive. Mechanically, seems like a better design, does require an adapter plate. Others can likely speak to the cleaning and maintenance of the pivot and track.
Sidewinder - lighter and less expensive. Works with conventional 5th wheel hitches, which are lighter and easier to remove when needed. They work, they last, the turret requires dropping and re-greasing about every 6 months (for me it did, others mileage may vary). The design and mechanical forces transmitted through the turret always bugged me. But again, they work as advertised. Requires adjustment of the "wedge" if someone else tows it, or removal and pinning to keep it from pivoting for a conventional pinbox approach.
When I purchased my Springdale, I was pulling it was a short bed 1/2 ton. I couldn't afford the weigh penalty. It saw use monthly for 2 years and 9 months, until I got my long bed truck. It is now pinned and acts as a conventional pinbox. For me, money well spent.
Hope this helps!
