oils are made from a base oil improved with additives. the higher the "synthetic" claim, the more of the "base oil" is replaced by "harder" man made or improved fractions... therefore fully synth is fully man made / processed. this has naff all to do with "bike or car" applications. (and is instead looking for air release, shearing (from gears), heat, acid and base resistence (not an exhaustive list my any means) - the longer the oil remains in good condition, the longer it does its job. obviously this is important in highly tuned engines, (Race and high revving road).
my personal rule of thumb - if most of the time is speant below 8K (on bikes), use mineral, above use semi, if racing (not track days) use fully synth.
the clutch probs come from friction reduction additives that are added to car oils - these esters (i think) bond to the internal surfaces to provide another molecular layer of protection. If your bike has a wet clutch (one which runs in the engine oil) these additives bond to this as well, reducing the coefficient of friction of the clutch, (not what you want - causes slip).
Bike oils leave out this additive. that is the only difference (well, it was in the world leader oil firm i worked for). If you have a dry clutch (ducati's and all cars) this isn't an issue as the oil doesn't come in contact with it. a newer clutch is "rougher" so will resist it more. If you ride gently you will notice it less, BUT the damage is still done.
had a boss who owned a training school who proved this theory brilliently. 10 bikes, bulk car oil (despite advice!), all get a service, all need new clutchs due to excess slip within a week!
so, IMHO. for 99% of the bikes on this page there is no point buying anything more than mineral bike oil. change it often (when it needs it not when the book says!). Most important: Always keep it topped up (will make it last far longer as it has longer "recovery" when your engines working)
and no, the price difference is not justified.
gosh, rant, sorry! hope it answers the question though!