OP, much like you I had been on the fence for years about getting a
chipper. Like so many others my only experience was with the small 3" self powered units which left me completely frustrated. I never actively looked for a unit but would see deals come and go from time to time but never the right combination of good deal, free time, and close location. That is until a few months ago. I stumbled upon a poorly worded ad on craigslist for a "used", really like new 6" Wallenstein hydraulic feed
chipper. All the used market here migrated to FB marketplace a couple years and craigslist is pretty dead, combination of that and a very non descriptive ad let the thing set forsale for a couple of months before I noticed it. Gentleman was going to pull the ad and have the dealer he bought it from put it up for sale on the day I called. Sometimes we just get lucky I guess. New retail on the current model is almost $11k, I paid the going rate for a used
Woodmaxx in this area.
I can't say the hydraulic feed is must have but it certainly is a nice to have in my limited experience. In my case I have 2 sons who are both learning and like to help. The controlled feed slows things down which helps. Doesn't mean that all the same safety precautions don't need to be taken though.
Pros/cons of each have been covered pretty well already, only comment is 6" plus units do seem to be much more accommodating in what will feed easily. In the end I don't think a
chipper is for everybody but only one way to find out is to try one. Personally I don't think I will be a long term owner, much like the original owner I bought from. In his case and mine all of our ash trees are dying and chipping at least a portion of the wood that is to small for firewood is a nice option to add along side leaving them to rot in the woods. I would keep passively watching for the right deal to come along and pick one up. If you buy smart you can always resell for +- a few hundred dollars.