Glycerin or Glycerol is made from rendering lipids in adipose tissues. Vegetable glycerin is the same chemical, but created from plant fats (usually soybean) and a complex chemical process. Ultimately, they are both exactly the same chemical, so there is no difference between vegetable glycerin and others. Some vegetable glycerins are occasionally not quite as pure as the purification process is kind of expensive, and "natural" companies can sometmes overlook the last part to save a few pennies. However, if you get lab or medical grade, it is indistinguishable from animal derived glycerin.
So, what it comes down to, really, is how you feel about animal products. In the case of making cleaning solution, I myself buy medical grade stuff from the pharmacy. The labels don't tell you the source, but I suspect plant based, but as I said, it's not different than animal based if done right.
Glycerin is glycerin, so either choice will work.
One thing to look out for, is that often glycerin sold for cosmetic purposes, may have perfumes or dyes added to it to give it color or make it more attractive to consumers. It's unlikely that it will effect your cleaning solution, but you may find the smell disagreeable if you are spraying it, so look for glycerin with nothing added in. Common liquid dish soap is 80% glycerin and works about as well as the lab grade stuff in making cleaner or reducer.
Where I live tho, a big bottle of it from the first aid aile at the chemists/drug store is about a buck. Wheras a big bottle of dishwashing liquid is about $5, so it is cheaper and no weird smells.
So any will really do. I'd probably buy some aimed at first aid or for dry skin, but with no perfume or colorant.