Types of carbon fibre frames

In general, what is the difference between a companies lightest (most expensive) carbon fibre frame and the next lightest (2nd most expensive)? I'm sure this varies between manufactures, but are there a few things that usually stick out (e.g. if both are monocoque, is the heavier frame stronger, stiffer...etc.).

For example, Opus Bikes (small company in Canada) has their lightest at 875g (monocoque with super light T-1000 carbon fibre with 1k weave finish) and the next lightest at 1125g T-700 carbon fibre with 12k weave finish). I'm not sure what this means (though I will be speaking to an LBS at some point in the future).

I'm interested in strength and comfort over the lightest weight or stiffest frame (I only ride recreationally including a few centuries a year). I'm also looking at other frame materials.

Lighter frames may have less CF. Lighter frames may use a different CF. It's fruitless to compare the light frame from one company to a frame from a different company and draw any real useful conclusions, without knowing the exact layup schedule for each frame. In general though, a heavier frame could be expected to be a bit more robust, everything else being equal.

Frankly, the weight of the frame is the last thing I'd consider. Foremost in my mind would be fit and how the bike felt when I pedaled it. Frame weight makes so very little difference in how a bike performs. In fact, unless your normal ride route goes up a lot of 18% or so grades, you'd be hard pressed to notice any difference even with a stopwatch. So, my priorities would be to buy the one that fit well, felt good when I pedaled it, fit my budget, and really pressed all my pleasure buttons.

__________________
Sex is horrid
Pain is Fun
I cut my fingers off
One by one

here, here, good response, I think that too many bike buyers think too much about weight, spend the money if you can afford it. As I have always said it is cheaper to lose 5 pounds off my big butt than a few ounces of a bike.