Seems every comment here is wrong or comparing to SC2.

• Bio is much harder to control, eating away commands that could go to other things. Bio isn't actually that bad, it's just not like SC2 where you can select them all at once. In the late game Terran would have something like seven control groups for bio and one for vessels.

• You need vessels for EMP and/or detection, so you'll take the mech tech path no matter what.

• Early game bio can not handle an aggressive Protoss player. A tank will zone out harassing dragoons. A dragoon with the range upgrade can shoot a bunker while staying out of range. You can get bio range upgrade to offset this but then you've dumped twice as much money as a tank with siege into an academy, range, medic(s), possibly stim, and subsequently scanners otherwise a DT will instawreck you because you won't have vulture mines. If you do get vulture mines, again, you've opened the mech tech path. Just get a tank.

• Storm and reavers will desecrate an entire bio army instantly

• Dragoons with zealots make mincemeat out of any bio army.

• While considered stronger in the early-mid game, Protoss has fewer units in exchange for more power/health per unit at Terran's bio stages. This makes tanks and mines much stronger.

Basically, TvP requires you to open the mech tech path early on, as it's the most cost efficient attacking and defending method versus most Protoss attacks.