The PT860 has for me the same absolute shave, but is your goal faster. Shaving with the Arcitec model lasted nearly twice as long with me.
When skin irritation I have found no significant differences.
Cleaning the PT860 is much better (compared with Arcitec). The beard catching chambers are much larger, so that a cleaning is needed only once a week. You can clean both units with water.
Problems with locking the shaving head does not exist when PT860.
I can not understand, therefore, that the Arcitec model performed better in Stiftung Warentest (albeit minimally better grade). From the point that the cheapest model costs Arcitec more than double, the PT860 is an absolute bargain with a top performance.
Single note: the Spartan accessory consists of a brush and a cover for the razor. So if this more expected (pocket, wall mount, etc.) must resort to the more expensive models. For me it was not a problem as I had Accessories of equipment (also Philips).
Conclusion: just buy it at a good price.