The Rocker has been around for some time now. When it was first introduced it was hoped (by Troll anyway) that it would become the alternative rope access back-up device to the Petzl Shunt. Extensive testing was carried out by IRATA and the UK's HSE but it was concluded that it offered nothing better, in terms of safety, than the Shunt, other than conformance to an industrial EN standard, EN12841A, as opposed to EN567 for the Shunt (EN567 being a mountaineering standard for ascender devices).
Getting equipment to pass an EN standard test is one thing, whether it will work or not in the real world is something completely different. I carried out extensive testing on the device with a number of different test weights and found the device to be ineffective with anything other than the 100kg test weight as used for the Standard. Very worrying. The main issue with the device, or indeed any device that is either required to be towed down the rope or is free travelling and simply requires you to overtake the device to make it engage, is that you won't necessarily overtake it or, more likely, in the event of a fall you will simply, by way of a natural reaction, grab the device or grab the rope above the device rendering it ineffective. There have been at least 2 fatalities and numerous other very serious accidents in the rope access industry due to people grabbing the device in a fall and usually not letting go until they hit something on the way down.
The UK HSE in October 2014 stated at an IRATA Health & Safety Committee meeting that they would recommend against anyone using towed type back-up devices or indeed any devices which could be rendered ineffective if grabbed. From an industrial point of view there are really only the 2 x Petzl ASAP's which will work in any eventuality.
It was at this same meeting that the HSE talked about the most recent work at height accident they were investigating which involved two fully equipped fire fighters. They were doing a snatch type rescue, lost control of the descender and the Rocker simply slithered down the rope until they both hit the deck, both suffering serious lower leg fractures. The device was rated for rescue loads of up to 250kg.
IRATA, in its infinite wisdom, decided not to publish the comments made by the HSE in the meetings minutes, possibly because the Chairman (and minute taker) of the committee still uses Shunts in his operations.
The Pro Allp Tec was designed by Dave Allport (formally of Troll). Its primary use was for mountain rescue, particularly allowing a controlled descent with a horizontal stretcher by the attending barrow boy. A slow, constant descent rate can be set with the wing nut and if you need to get past an obstruction, e.g., an overhang, the handle can be deployed to speed up the process, reverting back to a controlled descent. The wing nut can also be set to allow the handle to be operated as a standard auto lock descender. They are actually very good for what they were designed for. They are a bit big and heavy for caving though.
Both the Rocker and the Pro Allp Tech are made by International Safety Components (ISC) in the UK.
I'd stick with your Stop.
Mark