It looks like it's due to his computer having a much lower CPU benchmark than yours. Lower benchmark means lower claimed credit per CPU second. The time difference isn't huge though because LLR doesn't have any advantage on a 64-bit OS, but your CPU benchmark will still be much higher.

I'm not exactly an authority on this stuff though... still seems a bit weird to me.
____________

Well, his computer is definately claiming lower than normal. I've seen low claims, but this is extremely low. Reason: unknown.

This is on all types of WU's too, not just woo's
____________

Reading the following page might give you a few of the answers you are looking for regarding credit computation.

http://boinc.berkeley.edu/wiki/Computation_credit

The basic hourly claim the client submits with a Result to the project servers is the sum of Whetstone plus Dhrystone values of the last Benchmark divided by about 480 (it varies slightly with processor and OS). Thus for instance (2,000 Whetstone + 6,000 Dhrystone) / 480 = 16.66 hourly claim. This exact value will not always show on the results listing of projects. It is often substituted by their own pre-assigned credit value.

This time it's on Cullen LLR WUs. It crunches these at 127k-129k sec's per WU and is claiming 630 credits for each. My other machine is processing them at 131k-133k secs each claiming 960 cr.

One thing to note when considering the discrepancy between fixed and variable rate projects, is there seems to be a premium assigned to the variable rate projects in the actual credit granted. Standard BOINC procedure is to simply award the lowest credit claimed, but at Primegrid, the granted credit is generally higher than both of the claimed.

There doesn't seem to be a consistent ratio, but it does close (or even overshoot) the gap between 32 and 64-bit projects once you also account for the 1.7x advantage.

For example, one of the Cullen LLR done by your Q9550 has validated, and received 1290 credits instead of 963, and the doublechecker only claimed 692 credits.

I obviously don't personally know the inner workings of how Primegrid awards its credit, but looking at all of these factors there does seem to be a method to the madness.
____________

Since you were curious; the Cullen my machine did finally validated, and it recieved 1084 credits.

Doing a little bit of research and math, it looks like Primegrid assigns credit for LLRs based on the average of the claimed credit of both checkers, times some sort of correction factor. Checking a few WUs from a few different Subprojects showed that the factor seems to be set at about 1.5. (Cullen all appeared to be 1.55, PPS was about 1.4, and I checked two Woodall that were 1.4 and 1.5).
____________

There are also known differences in the BOINC benchmark results for different OSes and different BOINC client versions. If i remember correctly then there are BOINC client versions out there, especially older versions, which result in much higher benchmark numbers on Linux than on Windows for the same system.
I think there are also ways to manipulate the benchmark results (e.g. optimized BOINC clients)
Those are some of the main reason why many projects switched to fixed credits or credits based on calculation steps done by the project application for a certain WU.