I’m talking about frappucinos and mochas, that kind of thing. Obviously a regular coffee would taste the same in any size.
Why would the size of the container make any difference?
The ratio of ingredients is different.
Scroll down to the second chart here, just above the heading “Ice”. You can see that the way they have to add a full pump (or not, in some cases) when moving up a size makes it impossible to keep the same ratio. Same is true of the shots of espresso: the grande and venti have the same proportion (1 shot per 8 oz. of drink), but the tall is much more diluted in that respect, as it only has a single shot for 12 oz of drink.
Overall, the tall almost has to have a weaker flavour than the others, both in espresso and syrup. But that might be all right (I don’t think I’ve ever ordered one, so I’m speculating) as the flavour can be a little overpowering sometimes.