When i was researching wfp before making the jump from trad to wfp, i thought the pf trolley was the best on market. I was going to start on trolley 25l system for upstairs only with it n trad downstairs. I was adviced that most upgrade to a van mount later so skip middle ground. Im thankful i listened.
All the faff sorting watet drop off points n filling up or carrying trad around for downstairs, gives me a headache thinking about it.
After a yr now on wfp, never had need for a trolley. But ive just taken delivery of gardiners back pack for purpose of soft washing and thats a great piece of kit. As its cor soft washing im just carrying it (still young enough to do so).
Personally i think all the trolley systems are very expensive for what they are as these threads show. Many have adapted their trolley or built one up. The onky advantage is to buying one is that it looks more professional depending on your diy skills.