Having a sensible process is an advantage. In fact in order to allow you to survive long enough for the time advantage to come into effect it is probably a necessity.
I actually believe there are many sensible styles of both investing and trading. Clearly people have made great money out of both macro and micro trading and great money out of both value and momentum investing. So I will not say any particular system is inherently better than another, save only the system you use needs to fit with your skills and temperament.
I used to kow a guy who headed up the FX desk for a large Investment Bank. He positively needed to hold a position with volatility. If for some reason he had closed all his positions and we were going out for dinner you could be pretty sure at some stage in the evening he would call in an order to the overnight desk as sitting with all his positions closed out, made him feel uneasy. Clearly for him the idea of buy and hold was anathema, but it worked for him. I on the other hand do not understand currency trading other than as a momentum trade and do not do it.
I would however say that in whatever process you follow it is vital that you understand how your system deals with risk. I know a couple of traders that operate on the basis that the capital at risk they place in every trade is no more than 1% of the portfolio. Equally I know at least one growth investor who holds no more than 10 positions and believes he manages the risk by being very involved with the investments. In a recent filling in the US it was suggested that Monish Pabrai, author of the Dando Manifesto had in his main multimillion dollar fund only 3 holdings and one of those was cash. Very much the Buffet/Munger dictum of when you think you have a good idea go all in. "When it is raining money, put the bucket out".
Having a process that you understand and can be content with the risk management in the process applies just as much for professional investors as to retail investors. Most of the money stolen by Bernie Madoff was from professional firms that skipped reasonable due diligence because they were attracted by the regularity of the returns claimed.
Proper processes also help manage some of the risks of ignoring mistakes or dealing with mistakes by swinging from one extreme to another. If you have a clear process it allows you a lens through which to consider whether you made a genuine mistake that needs correction or whether you were operating a good process that has on this occasion been subject to the behaviour of the market.
I also think that it is unlikely that you have a proper process if you cannot clearly put it down in writing and have someone else understand it and agree it is sensible. I throw darts at the paper is a process but it should not survive an independent review for sense.
This does not mean that a process cannot evolve or even fundamentally change as knowledge grows or markets develop but again changes as incorporated should be capable of clear definition.
I would also add that for most private investors consideration of the process of investment should reflect some element or at least consideration of asset allocation. I do not propose to get into asset allocation here as I believe as with investing process there are many ways forward. But should the area be one you want to know more about I suggest you type in Google “Ben Carlson asset allocation” and start looking from there.
Of all the Advantages having and operating a Process is the one that rests entirely with the investor. If they choose not to develop one or choose not to implement it, that is down to them and them alone and a proper process is to my mind the big divide between the serious investor and the player. Given investment is a zero sum game I do not think you should be investing without a process that you feel confident with.
That is not to say that you need a massively complicated process. I saw one recently that had about 40 steps and I think allows you to buy nothing, so it is pointless. Also some of the very successful quant investors, such as Cliff Asness CEO of AQR ($250bn under management) and Meb Faber of Cambria say you can get at least 80% of their above market return from only 5 factors. And there is at least one strategy that predominately transacts on the relative momentum between equities and bonds over the last 6 months.
So Process need not be complicated but I would consider it to be vital.
“Look around the table, if you don’t know who the sucker is, get up and leave”. Thomas Preston