Should you buy the Drake Transitional or the standard Drake?
This is the same toilet with two tank options. TOTO's model numbers make it explicit: the standard Drake tank is CST776 and the Transitional is CST786. The bowl, the TORNADO FLUSH nozzles, the CEFIONTECT glaze and the 1.28 gallon flush are shared.
There is no performance difference. A plumber asking this exact question on a trade forum got the same answer: the Transitional tank is decorative and has zero impact on how the toilet works.
There is one small practical benefit. The Transitional tank has a flat top, so you get a usable surface for a spare roll or a candle. The standard Drake lid is contoured and does not hold anything.
Price does not follow a single direction, which is worth knowing before you assume the plainer one is cheaper. As a bare 1.28 GPF toilet they are within $3 of each other. With an S2 washlet the Transitional is $161 cheaper. At S5 they are level, and at S7 and S7A the standard Drake is about $45 less.
Range is where the standard Drake pulls ahead. It has 14 models against 8, and it is the only one offering a 1.6 GPF flush or a round bowl. If you need either of those, the Transitional is not an option.
Choose on looks. The Transitional suits a softer or more traditional bathroom and gives you the flat tank top. The standard Drake suits a plainer room and opens up more configurations. Then check the price at your washlet tier, because the cheaper one changes depending on which seat you want. See the Drake WASHLET+ range for the fitted combinations.