I am sure you are getting fine results with your method, however the key as i said is the ability to match a pre determined benchmark for various measurements (1) and to be able to get the same results over and over and over (2).
A jobo machine, along with the correct drum will give you results that are within range of the above mentioned benchmarks: Density, Eavennes, cleanliness and a few other things. You will be able to repeat those results every time you use the machine with the same film\chemicals to produce those "perfect" or more accurately within range results.
The bottom line is what you consider to be "good" and the fact you see it as consistent from run to run as the same quality of "good" must be compared to established standards of quality. For most of us, even with a trained eye there may only be a marginal visual difference in smaller formats which increases as the size of the film increases. Which is where the benchmark is important, and where a Jobo delivers.
There is a long and boring technical explanation as to why this is so, but the short answer is - after you start using a Jobo (manual or automatic) you will not go back to hand processing ever again. The ease of use and time saving is only second to the results, that will most likely blow you away. Another wonderful thing Jobo machines allow is higher\lower capacity with minimal loss or waste of chemistry.
When you go out with your side pack loaded with 20 4X5 holders and you want to see what you have done shortly after you get home, a Jobo drum that hols up to 12 sheets of 4X5 in a single run will not only be a cool thing - but will be a huge time and effort saver. same goes for a 10X 35mm tank or 8X120 and so on.
Automatic machines are those models with the designation - ATL (the A standing for Auto). These tend to be slightly more expensive and or larger to the point that a home user might not consider them an option.
The smaller ATL machines (500/800/1000/1500) are some of the greatest mechanical wonders of the 20th century, but those tend to be expensive.