In short higher gear ratio will retrieve more line (quicker) per turn of the handle relative to the size of the spool (bigger spool more line length per loop of the spool) = more lure speed.

Lower gear ratio will give more torque so sometimes better for jigging (as far as cranking up fish) but higher ratio (again relative to spool) will give you a faster retrieve so can be a bit of a balancing act.

Can be a bit of individual preference as to whether a high retrieve or lower is best for jigging. I find torque or "cranking power" a little bit of a furphy as you shouldn't crank with just the reel anyway and use the rod to lift and wind down onto the fish. That being said a bit of torque/cranking power does help to keep their head coming up when you're talking the likes of Doggies, kingies and sampsons etc. as the jigging target

Cheers

I've got a stella 8000PG (ratio 4.9:1), and that's perfect for jigging whether for sambos or larger demersals. I think the higher ratio is more suited to casting/popping where you need to retrieve a lot of line fast in between pops, without working too hard.

for the stella 5000, I think the PG will also be most suitable for lighter jigging (4.6:1)

in saying that it probably also depends how you prefer to jig, I know some guys who prefer to make very long fast strokes which would probably be more suited to a higher gear ratio?? So personal preference probably has a lot to do with final decision

Gear ratio critical for jigging. Huge mistake is to get a high speed reel for jigging.......you will hate it!!!!

Retrieve of 75 cm/crank on PE2 up to 90 cm per crank on PE5 perfect for jigging.

 Yes high speed is good for tossing metal slugs to Tuna etc. if that's your main target get the highest gear the 5000 has, the 6.2:1. I have the 2008 model and it's brilliant. One thing worth noting is that due to it still being a small reel the line retrieve per turn of the handle is not that extreme so you can jig with it. If you plan to do both evenly go the middle gear ratio. My personal thoughts on a reel of that size and through experience is the lower power gear is not really needed unless you wind fish in with outs using the rod or are solely jigging.

On the bigger reels the difference becomes a lot more noticeable as you are running higher drag and lifting larger fish/lures.

I also have the Stella 10000 as I got it for popping. When I use it for bottom fishing I do notice its more of a struggle then other lower geared reels I have around the same size or even bigger. Sometimes I wish I had the 8000PG as it has the lower relationship and slightly smaller spool making the line retrieve per handle turn much less and easier to fish fish with.

 How did my phone autocorrect "ratio" to relationship? Oh well sounds like you still made sense of that dribble!!!