When ever i had proportionals set on my racks in 80F room i had to set them ot 96+ to get just a 89-90 in the tubs.

Johnsons i set all of them at 92 and inside is 90-91. The tubs sit directly on the heat tape which the tape never passes 105F when it kicks on.

Room temps is where you base your setup off of. If you want a steady temp with little fluctuations get proportional. But which ever you chose, keep in mind they are man made and electronic that can fail. So dont buy the most expensive one with the piece of mind its safer.