SSD – Understanding 4K Random Read/Write QD1…32 and IOPS Values

Another thing to consider is that SSDs can, in general, be faster the more free space there is on the drive. From AnandTech: "You should buy the largest drive you need/can afford". For example, if you have 55GB of programs/data on the SSD, the 80GB Intel drive would (probably) retain more of its performance compared to the 60GB OCZ Vertex. (This is because an SSD should add free space to its pool of spare area, which ultimately improves the write amplification ratio, as summarised here.)

And as AnandTech (and the other review sites) discuss, it's only in rare situations that the Intel drives' relatively low sequential rates are a problem; the fast random read/write performance is more important most of the time.

Thanks James. It doesn't fully answer my question but there are some useful tidbits. To summarize some of the relevant parts of those talks:

SSD performance can increase by 10% or more as the "spare area" on the SSD increases.
Increases in spare area on MLC (vs SLC) is particularly good at increasing performance. Most of the SSDs which are reasonably big tend to use MLC, which has somewhat higher latency and lower write bandwidth, but comparable read bandwidth.

So drawing from this, it seems that a bigger SSD will probably have higher performance than a smaller SSD, unless the reason the smaller SSD is smaller is because it uses SLC or it has a higher percentage of spare.

This is mostly what I expected but it's nice to see confirmation.

Another useful but again not entirely comprehensive look comes from just scanning some of the tech specs on the web. For example I look a look at OCZ's page here on the Vertex Turbo. It seems that throughput does not come at all close to linearly increasing with drive size. It takes a jump from 30 GB to 120 GB to see a significant difference, and even then mainly for write speed not read.