The full synthetic I run in my tahoe, as well as, sell to my oil change customers is made by American oil. I believe some of it is private labelled under the MAG1 brand name. It costs me like $3.00/qt and is just as good as Valvoline Synpower or Mobil 1(i have the spec sheets every spec is within a couple points, and a couple points isn't going to make it a "bad" product). We used to be a Valvoline store until high prices started killing our business, so we switch to a "no name" brand that is just as good and half the price. So instead of paying $7.00/qt for mobil 1 i pay $3 for a product that is just as good. (7x6=42 3x6=18 plus $3 for a filter and Mobil 1 is $45 vs. American oil at $21 that leaves room for a 12 pack of beer to go with my oil change!)
Most oils come from a select few manufacturers(there is like 4 or 5 big companies), who all slap a different label on the bottle hoping you will buy it because some one told you that it was the best oil you could get. If the name means that much and you have money to burn then get it. It is much like groceries, do you buy the Great Value canned goods($.89) or the Green Giant canned goods($1.29)? Both probably come from the same field.
Also switching back and forth shouldn't hurt a thing, that is an old way of thinking. Also most oils now a days are good enough to be considered "semi" synthetics.(there are some that are still truely conventional) Valvoline conventional is good enough to be called semi synthetic by standards, but they would rather sell you Durablend at a higher price than tell you that the regular stuff is a semi synthetic...they just want more of your hard earned dollars.
ok i'll stop ranting about oil.. (p.s. i have been in the oil change business for 8 yrs, i have seen a lot of high priced products that get pushed on to the consumer all because of the name...i'm sick of it, mainly because most people work hard for there money and shouldn't be suckered into a high priced product that they don't need when a lesser priced one that is just as good could be used)