The base stocks in specific brands and types of motor oils are very similar. It's the additive package (including the aforementioned detergents) that separate them.
The argument as which is better, is one better than the other, etc has been an on going thing, and will continue to rage for the indefinite future. Primarily because of the relative newness of motorcycle specific oils to the marketplace and the lack of any real long term definitive test results.
In a nutshell, it has pretty well been established that all oils, offer short term protection and lubrication in a motorcycle engine. Tests that I've studied and read with regards to the various types of oils, how and when they break down under use in a motorcycle engine have been inconclusive in my mind. Could go either way, mainly depending upon the type of base stock.
The main thing that most all the 'experts' agree on is the friction modifier issue. If an oil is marketed and marked as an "Energy Conservation" oil it most definitely does contain friction modifiers. These additives give the oil a tendency to reduce friction between surfaces. Which is a good thing when we're talking about say, a piston and cylinder wall, but that turns into bad thing when discussing clutch plates.
The only energy conserving oils on the market are indeed automotive specific. Motorcycle specific oils and desiel engine oils do not.
Many riders, in an effort to be thrifty, not spend any more money than absolutely neccessary on thier machines, or to not pay for motorcycle shops outragous profit margins (rotflmao) use automotive oil, and most, especially those that trade bikes on a more or less normal schedule, get away with it. Many more use desiel oils due to the lack of friction modifiers. Heck, I know of several riders that use ATF in thier motorcycles gearboxes, have for years and swear they will never change.
The thing I have found through specific testing on my bikes is that a pure synthetic motorcycle specific oil remains consistant in make up and nature well past the scheduled oil changes. None of the oil samples I have sent in for testing show any break down what so ever at the recommended interval, or up to half again the suggested mileage. I've not gone twice the recommened mileage to do that test, and honestly probably won't! *lol* But up to a little over 6,000 miles I have never, not once, had a test result come back showing any negative results. So the extra $3, while not a huge concern to me in the first place, is even less so because I can, and do, go longer between oil changes with it.
Would the same thing happen with an automotive or desiel oil? Maybe. Even probably. But my personal nature is to use products designed for the particular application. I don't use dish soap in the washing machine or kerosene in the parts washer either.
Also, for what it's worth, let me clear the air right now as to the costs of motorcycle specific oils. I'm tired of reading and hearing from folks that don't really know wat they are talking about in relation to the margins on these oils. Truth and fact is that there is no more margin on oil than on anything else you'll get from a shop or dealership. Sorry guys, it's a fact. MSRP pricing is set by every frigging body but the retailer and the ONLY way for us to make any additional profit per item is to buy cheaper, i.e. in bulk. In fact, many shops and dealerships these days view oils and tires as fast moving, 'loss leader' items and sell below, if not way below MSRP in an effort to draw customers in. In my parts department we mark up on road tires $20 over cost, off road tires $10, and most oils a whopping $1 per quart. Truth is, if I can't make at least that much, and my accountant says thats not enough, on these items I don't need to devote the shelf space to them.
In the end, use whatever makes you comfortable. Think about how long you want to keep the particular bike. If it's a 'short timer', screw it, as long as whatever you use is slippery you'll probably be fine. If you plan on keeping it and putting a lot of milage on it, do your own research and come up with your own conclusions. My bet is that if you do that, you'll be using oil with a picture of a motorcycle on the bottle. ;)
Good luck!