I just finished a trip on Silhouette, our first time on X. We (especially my husband) were underwhelmed with the MDR dinners. The service was find but the food, especially the side dishes like rice, just wasn't that good. We had dinner our last night in Qsine and it was far and away better than the MDR.
On the other hand, I was pleasantly surprised by the OVC. Aside from one MDR breakfast we ate all our breakfasts and lunches there. The food was fresh and tasty and if they didn't have it, you didn't need it. So I can see why some people prefer dinner in the OVC, especially if they just want to eat and get on with their evening.