Although the monster does go through a great metamorphosis in learning about what it means to be human, Victor Frankenstein is greatly changed by his experience and his introspection on life deepens in humility as the book progresses.
Therefore, even though the monster changes and acquires more human qualities which allow him to think critically, Victor Frankenstein surpasses him in this area. In the following passage, Victor admits that he wasted his life on a project that was born from his egotistical tendencies.
"All my speculations and hopes are as nothing; and, like the archangel who aspired to omnipotence, I am chained in an eternal hell. My imagination was vivid, yet my powers of analysis and application were intense; by the union of these qualities I conceived the idea and executed the creation of a man. Even now I cannot recollect without passion my reveries while the work was incomplete. I trod heaven in my thoughts, now exulting in my powers, now burning with the idea of their effects." (Chapter 24)
Victor realizes that he attempted to play God, and for his ambition, his desire to achieve this feat, he now suffers. This quote symbolizes how Victor Frankenstein has changed and become much more contemplative, a gifted scientist, he should have put his brilliant mind towards helping humanity fight disease instead.
The monster no matter how intellectual he becomes is still a primal beast.
Oh, most definitely the creature. Think about all of Victor's actions - they are not from careful thought, but from emotion. When the monster awakes - Victor runs away. When Justine is in jail - Victor is too fearful to confess and save her. When the monster stalks him - Victor's fear make him determined to foil the monster's wishes. He does not consider all the consequences - he makes assumptions, which invarely prove to be wrong.
The monster, however, spends time studying people and "experimenting" with contact and exposure. He weighs his options, decides what he wants (a mate) and decides the best way to get it. He methodically and patiently baits Victor, intimidates him, and plots to make him pay for denying the wish. This passage, in which the monster questions his own existence and the purpose for it, shows his level of critical thought:
"The words induced me to turn towards myself. I learned that the possessions most esteemed by your fellow creatures were high and unsullied descent united with riches. ...And what was I? ... I knew that I possessed no money, no friends, no kind of property. .... I was not even of the same nature as man. I was more agile than they and could subsist upon coarser diet; I bore the extremes of heat and cold with less injury to my frame; my stature far exceeded theirs. ...Was I, then, a monster, a blot upon the earth, from which all men fled and whom all men disowned?
While Victor Frankenstein is the "intelligent" and "educated" one, he is controlled by a greed for power and MORE intellect. He does exhibit moments of critical thinking; an example of this is when he destroys the second creature. Towards the end of the novel, Victor is driven by vengeance - not intelligence - while wanting to catch the monster.
It is the monster, or daemon (as referred to in the novel) who really shows critical thinking. He is learning about society and making judgements, learning that he is judged by his physical appearance. He is teaching himself how to read - and incorporating his new found intelligence into his belief system.