Relay computerswhy so few 16

Is it correct to simply say that one or the other of vacuum tubes or relays would be more reliable.

In the average consumer product, relays were probably far more reliable. But that was also virtually always a "minimum initial cost" design too, so the tube circuits were never intended to have long term reliability simply because that was very expensive.

At a commercial level, for example in telephone exchanges, there was some equipment designed with similar goals as the consumer equipment above, but others where reliability was given significantly more weight. When cost was also important (but reliability still the prime target), tubes would be more reliable. WECO, for example, often designed tube type equipment where the tubes lasted in excess of 20 years! Compare that to the mbuttive maintenance requirements for WECO relays, most of which had to be cleaned and-or adjusted with regularity.

On the other hand, if cost was no problem and reliability essential, sealed relays that never needed adjustment or cleaning were possible, and probably had almost the same low failure rates as vacuum tubes in equipment intended to last 20 years without maintenance. (Of course, the part count goes up with such designs, so the overall equipment may not be all that much more reliable, plus the physical size made many things simply impossible until solid state devices became available.)

--