Indoor plants may be warm and away from wind, but they rely on you alone for water
As part of the trial I grew a second set of all 17 tomato varieties inside a polytunnel. Most performed similarly outside and in, though almost all grew considerably larger fruit outside. This is because of near-unlimited access to water outdoors from (sometimes torrential) rain toward the end of summer. Splitting was a concern as fruit swelled, but few actually did, perhaps because moisture was so constant… suggesting I am perhaps too stingy with water inside my polytunnel.