We've had both kinds and I found the bosch screw one the best. The one we have a the moment has blades. It's ok but I would not buy it again.
The best advice I can offer is, whatever you choose, don't lend it out!
The blade on the Bosch we have can be turned over and used on the other side but it's made of something that can't be sharpened saying that, we are only just on our second blade and we have a very big shrubby garden, so it gets quite a bit of use.
with regards to your greenhouse, can you just get new panes of glass cut and get some clips from Amazon for now it would be cheaper.
thank you all again, appreciate your thoughts
We borrowed our neighbour's shredder recently, a drum crushing type from Lidl under their Florabest own brand. It was very good, coping with all sorts of prunings from brambles up to pesky alder saplings growing in the wrong place. It has a built-in container to collect the bits and it chops things up into manageable pieces good for either composting or mulching depending on what's in it.
Lidl sell them from time to time so I'm hoping they have them in again soon as I would definitely buy one. Otherwise an article in an old copy of the Sunday Times recommended a Makita UD2500 drum shredder for about £180 which seemed pretty good and cheaper and quieter than most other things on test.