A throttle just gives you the choice, was what I found. If you want to ride around entirely on power like a eMoped or something, then of course you can, and conversely you can just switch it off (and your ride will be tougher workout than on a standard bike), but you also have infinite instant options available to you in between those two extremes. It really is down to the rider and what they want or don't want to get out of the ride. PAS is really just predetermined throttle positionings that increase assistance within certain fixed parameters with pedal revs. If you can't manage your ride better than that manually with a throttle then maybe PAS is a good choice. Please bear in mind that I have only ridden cheap versions of all the eBike stuff, so there may be others that can tell you that if you spend 11k on a Specialised S Works Turbo Creo SL, the PAS is fantastic. LOL. But seriously, I can only really comment from my limited and narrow experience based on what I have used, and a purpose-built eBike in the £2000 range might have incredibly sophisticated PAS. I guess the best thing would be to go and try some. I hope all this has helped.