I'll disagree with you for these reasons:
"The difference in performance performance between a card clocked 250/250 and the same card clocked 275/275 is really only noticed during benchmarking rather than actuall game playability,"
The difference in performance between 128 and 64MB cards is even LESS.
" but you can simply clock the slower card to the same speed as the faster card and they will bench the same."
Sure. If you know that bios hack/ use tweaker program, and if your slower RAM will run stable. Of course, the faster RAM on the retail will OC higher than the LE RAM ever will, so that blows this argument as well.
"It is much more difficult to change the hardware however. You cannot make a 64MB card a 128MBcard"
Like I said, there's no real reason to want to.
http://www6.tomshardware.com/graphic/02q1/020205/geforce3-10.html
"These results speak very clearly. 128MB are practically useless in current games."
"Since there are big hardware differences between the 2 cards, I say THOSE should be your primary concern,"
Big hardware differences? Oh, you must mean those extra 64MB of RAM that have NO tangible benefit.
"not the fact that one is clocked slower than the other. "
I guess more importantly, how smart is a guy who pays TWICE AS MUCH for a video card to get EXACTLY THE SAME PERFORMANCE?
Enquiring minds want to know....