Though my company produces a single tiny data logger that measures
temperature, light, and humidity, I can say with relative lack of bias
that each type of instrument has its place. The loggers generally do not
give a visual readout on the spot, yet they are lower in maintenance, are
more accurate over time, and allow you to keep better records and perform
more analysis with logger data than with hygrothermograph data. Also, they
are less expensive (ours is $249 and measures temp, RH, and light). Unlike
other miniature loggers, ours was designed with the museum market in mind
from the start, to be just one part of an overall environmental monitoring
program. Most of our customers use a combination of instruments to fit
their particular needs.

John Hotchkiss
The Kiwi Group
508-563-2824