Here’s what St. Thomas Aquinas, whose feast the universal Church celebrates today, had to say on the excellence of the vow of obedience:
The vow of obedience is the chief of the three religious vows, and this for three reasons.
First, because by the vow of obedience man offers God something greater, namely his own will; for this is of more account than his own body, which he offers God by continence, and than external things, which he offers God by the vow of poverty. Wherefore that which is done out of obedience is more acceptable to God than that which is done of one’s own will, according to the saying of Jerome (Ep. cxxv ad Rustic Monach.): “My words are intended to teach you not to rely on your own judgment”: and a little further on he says: “You may not do what you will; you must eat what you are bidden to eat, you may possess as much as you receive, clothe yourself with what is given to you.” Hence fasting is not acceptable to God if it is done of one’s own will, according to Is. 58:3, “Behold in the day of your fast your own will is found.”
Secondly, because the vow of obedience includes the other vows, but not vice versa: for a religious, though bound by vow to observe continence and poverty, yet these also come under obedience, as well as many other things besides the keeping of continence and poverty.
Thirdly, because the vow of obedience extends properly to those acts that are closely connected with the end of religion; and the more closely a thing is connected with the end, the better it is.
Taken from the Summa Theologiae, IIa IIae, q. 186, a. 8.