This is something that has been on my mind lately and I have attempted to write a couple of posts on it but have so far failed miserably at finishing them.
A quick definition to begin things: I will be working with the idea that a sadist derives sexual arousal from inflicting cruelty and suffering on others. While a non-sadist may experience some sexual arousal from similar activities, I will assume their arousal is due to other related factors (e.g. devotion, symbolism, a fetish, etc.) and not directly linked to their victim's physical/psychological/sexual discomfort.
In order to keep this interesting, the idea of the non-sadist Domme will be a rather extreme example: while she doesn't get turned on by cruelty, she is completely indifferent to whether or not the sub finds things cruel as long as it results in her desired outcome. In order for a sub to experience a similar level of (albeit different flavor of) suffering, this Domme would have to be extremely demanding, whether those demands are realistic or not.
The differences between a sadist and our non-sadist can yield some crucial differences in the sub's experiences even if the activities remain nearly identical.
Chore: a sub is ordered to clean a room.
Sadist (S): She will want to make this task more difficult and unpleasant. This might take the form of messing the room up more or using restraints to make the sub's job more difficult (e.g. wrists chained to his balls). She can experience arousal/pleasure by being present and tormenting the sub but will still experience arousal/pleasure without being present and simply thinking about how much the sub is struggling.
Non-Sadist (NS): She will expect this task to be performed quickly and thoroughly. Her pleasure comes from having a cleaned room without any wasted time, so it is unlikely she will do anything to inflict direct suffering. However, she may order the sub to perform this task in an unrealistic amount of time, e.g. it should take 2.5 hours, but he is expected to finish in 1 hour with no decrease in performance quality. Failure to complete in time or to her standards will result in severe punishment.
Uniform: a sub is dressed as a maid.
S: She will want the uniform to humiliate and embarrass the sub, ideally inflict discomfort. This can double as an actual or hypothetical threat in regards to further humiliation, blackmail, etc. She is more likely to go with over the top styles, painful and uncomfortable heels, wrist & ankle restraints, posture collars, gags, etc.
NS: She will want his uniform to represent his submissive role as well as his competence in fulfilling it. Being properly maintained and tidy are paramount. It will likely be something she finds aesthetically pleasing and suitable for his role.
S: She enjoys his sexual frustration and the constant mental suffering of earning release. Even if she doesn't plan to allow him release, she will keep the idea of release alive in his mind simply to witness his disappointment when she takes it away. If she keeps him contained for a long enough time, she might even make him beg to be milked.
NS: She is indifferent to his sexual needs. Chastity turns him into a non-sexual entity. Release isn't spoken of or even implied with the possible exception of maintenance milking.
S:She punishes him regularly to make him suffer, even if he is constantly suffering. Punishment can be used to inflict more exquisite forms of suffering than are present in normal day to day activities.
NS: For her, punishment serves a purpose: break any resistance and instill enough fear to keep him motivated. To achieve these ends, punishments have be very severe.
By now, you probably have some idea of which type of Domme you would rather fantasize about. While both may "do it" for a sub on some level, I have a feeling which one "does it more" is strongly linked to a submissive's self-worth and confidence in their abilities to serve/please the Domme. I could be wrong, but it seems like a sub who is fully confident in their abilities would be less fearful of a non-sadist that may make things difficult, but rarely impossible. If a sub is constantly afraid that they cannot perform adequately, the non-sadist probably provides a sink or swim environment conducive to their subspace. An abusive sadist can find creative ways to screw up a sub's performance no matter how competent they are. A sub that is fully confident but still craves fear most likely connects more strongly with the sadistic type.
If I'm wrong here, please let me know.
On another note, it's interesting when you look at how these types are portrayed in other fictional works. The non-sadist is almost always in some form of upper management position while the sadist is usually an underling who terrorizes someone even lower on the totem pole. e.g. CEO vs. Middle management, Warden vs. Guard, Super Villain vs. Top Henchman, etc. Apparently stereotypical representations seem to believe sadists aren't as ambitious or as capable of climbing the ladder as their non-sadistic counterparts.