There is certainly no difference between you and Immigration representative. If you hire one, you would still have to do the same things collect experience letter, write down duties, collect statements, browse your history of immigration, addresses..
collect educational degrees.
Only difference is they know the process while you would have to spend time to learn the process and small things which matter. It's also not true in all cases, I spoke to many consultants and I was never convinced those guys are good for me. One told, you have to have ECA for my wife even for PNP which is not the case, other told me .........
So, it's upto you if you have time and eye for a bit of analysis or you can blindly follow someone who may not be qualified enough. You have to research on that side as well to find a very good consultant you can trust.