I got the chance to taste both Mountain Dew and Pepsi Throwbacks recently. I feel pretty similarly about both of them as compared to their original counterparts, so I will fold it into one review. In both cases, cleaner flavor if you know what I mean (I have seen others describe the flavor as ‘clean’ as well, so I do not feel completely alone here). Also, the body of the soda was completely different, more of a wateriness to the texture. I am pretty sure this is a result of sugar making the drink less syrupy than the HFCS. Additionally, there seemed to be a little bit less of an aftertaste left on your tongue, but there was sweeter taste left on your lips when you lick them.
Speaking of sweeter, I think both drinks were sweeter than their HFCS counterparts, but the Pepsi was far sweeter than normal Pepsi. It reminded me a lot of the real sugar Coke or real sugar Pepsi Gold that I had in Jamaica (Pepsi Gold was a gold colored Pepsi variant that was a promo for the World Cup in 2006. It also apparently contained a hint of ginger not in normal Pepsi).
As I am not a big fan of Mountain Dew, Mountain Dew Throwback did not do enough for me to switch to it. I would drink it again though if given the chance to do so for free, and I would be interested in drinking it side-by-side with some Mountain Dew to do further flavor comparisons.
Pepsi, being my soda of choice, is what I am most picky about. I am not sure what to say really. Part of me is really used to the HFCS version and almosts misses the texture of it when drinking Throwback. That being said, I do like the extra sweetness and the other perks with the aftertaste. I think that if it stayed on the market and I got used to it, I would probably prefer it to normal Pepsi. I do not like it so much as to pay a premium to purchase it on more than a yearly basis though.