A simple question but what does it actually mean?
Lets start with the jigged one. Effectively the railing parts will be held in a “mold” or jig to hold the parts in place, whilst they are being welded. The jig will only allow the production with some serious limitations, much will depend on how its designed, height is usually adjustable, but spacing or gaps between upright bars will be constant. This means the gaps maybe set at say 100mm, which is fine if you have a gap that is 1500mm or 2100mm, as long as its a nice round number ending in 00mm its fine. You get an even gap between bars, from the wall or post to the first bar which is the same as the gap to the second and third bar and so on. When you have a wall gap of say 1550mm this falls apart, you end up with a gap from the first bar of 75mm to the wall and then a gap of 100mm from each bar there after until you get to the end where the wall to bar gap is 75mm. Another advantage of using a jig with a fixed spacing is that you can buy pre-made parts like circle and scrolls, these are manufacture in bulk and are far cheaper than hand made parts. Most are based on a 100mm gap between bar, this does allow a lot of designs that can be quite ornate but are way cheaper than a hand made version. If the jig is a fixed type that will only produce one size, its incredibly quick to build a railing, as everything slots into place. If its a more dynamic one its a little slow as there is a certain amount of measuring and setting out that is required. Sadly not all wall gaps are the same.
Hand made railings,
this is simply making it free hand with out the add of a jig to speed up the process, depending on the railing design this can sometime take twice as long to produce, and obviously that has an effect on the price. It does allow you to over come the issue of bar spacing, using the example of 1550mm. Set the spacing out at 96.875mm, and you have a nice even gap from wall to first bar and all the way to the end. You have to measure each gap and mark it out on the horizontal bars, then hold each bar in the correct position whilst it is welded. The end result is much more pleasing to the eye, but the cost is higher due to the time taken to produce, along with the additional cost of getting a drawing to work from. In terms of design its almost limitless what you can come up with, but each part like a circle would have to be formed by hand to fit the bar spacings.