I should explain my reason for asking my question.
I currently have system panniers which do not hold very much and are not the most useful of things with their shape and nooks and crannies.
Looking at ali panniers but don't need top quality stuff as no plans to tour the world, go off-road etc. Just want an every day set that have more usable space.
It still doesn't make it an easy job to recommend one type over another.
There are so many things to consider apart from what you have told us. For instance, do you want panniers that are easily and quickly detachable (either for bike cleaning/maintenance or because there are times that you don't need them on).
Is over-all width an issue either for peace of mind, access to bike parking or again would they need to be detachable to get the bike into its nest every time?
What about security of the panniers when fitted and the contents when left?
If you do a trip, alone or with a pillion, what sort of capacity do you anticipate requiring?
Sorry, I'm not being awkward but it's impossible to know what your requirements are. You'd be much better off spending some time looking through the various threads about panniers to see what the available options are. Then you need to make up your own mind as to what suits your intended use.
What I would say is take no notice of the "I love mine" comments. Few people are honest enough to report that they've paid good money for a pile of shite or that they made the wrong choice.
Try and read just the stuff about how they fit, how secure they are, how water-proof, easy to remove, re-fit even repair or get spares for. Then see what suits you best before fainting when you see how much they cost (really cheap ones look it when it comes to the way they fit).
Few (if any) are pretty so you can safely ignore the comments about how they look and be guaranteed that someone, somewhere will think that the ones you like look like shite.