Noo, Synthetic oil will provide better protection in engines running hotter or to reiterate, provide better protection above 250-280 degrees. So if your daily driving during the week consists mainly of stop and go traffic then yes, otherwise not necessarily.

Standard/conventional oil's have quite a bit of "junk" in it as k20eg said, they have sulfur, wax, etc. in them which synthetic oils wont have.

Synthetic oils are thinner as well, not to be confused with viscosity. In a vehicle where oil pressure may be say, 60 psi at around 6k rpm, you'll see roughly 45 psi.

Now, whether or not to make the switch. This depends upon an engine really and it's gaskets, seals and rings (since rings are essentially seals). Conventional oils with all their junk in them, will promote to gasket/seal swell. If this has began, then switching to a synthetic probably isn't a great idea as you'll likely start burning it off fairly quickly and/or leaking it. Let alone switching brand oils altogether, regardless if synthetic or not. So if you used conventional for awhile and then switched to synthetic oil, sure, you are probably seeing smoke as a result of this. (ie. seals, gaskets, etc. get "used to" a certain oil for the lack of a more molecular science explanation)

I always recommend for new builds (after the first 500 miles of running on non-detergent conventional) for customers/people to switch to synthetic (and stick with it). I do scratch my head a little at those that like to perform 3k mile oil changes when having only ever ran synthetic as this simply is not needed, even if you're running a turbo. Oil filter change, sure, go for it, but..

Now, canola oils are being produced right now that outperform both synthetics and conventional oils (yes, I follow damn near every aspect of vehicles - thus oils). As ethanol/bio become more readily available (and there is less corn to eat), I'm sure you'll begin to see these lubricating oils available as well.