I am not a huge fan of numeric ratings as an absolute though I do think it makes a nice starting point.
If you are comparing within varietals and one wine is a 95 while the other is a 78, pick the 95.
However, there is a bit of bias in any system that reflects the yearnings of the judges or authors of that system. While I am not an expert in wine, I know what I like. And one situation particularly shows me a lot. That is the issue of oaked chardonnays. When a chardonnay is produced in the small area of Chablis, France, or even in the larger area of the Maconnais, it usually spends a very short time (perhaps as little as three months) in oak casks. Because of this, such chardonnays come off svelte, crisp and refreshing.
California also produces fantastic chardonnays - with its climate making very dependable wines. Alas, about fifteen years ago there arose an arms race in Calchards to see who could produce the fullest, most complex chardonnays. This led, naturally, to oaking such that a Calchard may spend up to a year in oak casks with the oak imparting various flavors and textures to the resulting wine.
Eventually, oenophiles started describing Calchards in terms previously reserved for red grapes, and heavy ones at that. Terms like fullbodied, substantial, chewy, big in the mouth, lush, earthy came to describe what - in my view - can be and should be one of the most nimble and subtle of grapes.
And, egads, eventually claims went out that Calchards are "better" than French Chardonnay. I have never accepted this idea, though I do enjoy many Calchards. Even so, to me they should be given their own varietal due to the non-chardonnay manner in which they are treated.
A California chardonnay is like a busomy, boisterous fun woman that can both delight and overwelm with her lack of subtelty. A true French Chablis can be like a lithe French woman, polished, chic and appealing with her trim beauty.
So, to my unsophisticated palatte, the ratings are a ROUGH guide at best. I probably cant tell the difference between at 94 and an 89 when comparing varietals. On the other hand, I know what I like.