Some poker authorities recommend standardizing your bet sizing, thinking that varying your sizing allows opponents to read your intent — and therefore your range — more accurately.
Predictability is a very bad thing, but don't assume your opponents are accurately reading your sizing. Many players can't read your sizing's range. Also, if you apply a few deceptive plays, good readers will make errors and/or lose their confidence in their reads.
Accurate bet sizing based on your opponents' ranges and tendencies will extract optimum EV. Usually, when value betting a hand with no cards to come, you want to bet the amount that your opponents' calling will generate the most EV.