I seem to recall reading a technical review about solid state drives that included a pair of hard disk drives in a Raid array in the benchmarks. If memory serves the ssd's were all faster than the two hard drives. Unfortunately I can't remember which web site published the review.
EDIT - I think the answer might be over at AnandTech but their search feature isn't working right now. I'll try again later.
looks like you forgot to do a little research first. i'll highlight what you should look for.
i know there are charts out on the internet which detail exactly how fast each of those drives is.
once you get the individual numbers for both drives then figure that for raid 0 your performance will increase in the range of 30-60%. of course the exact performance will vary depending upon what you are doing.
also look at how each technology compares. for example, which type of drives are better at transfering large files, small files, random i/o and then compare with what you will be using the drive for.
in general either solution isn't a bad choice.
one benefit of going with the raid0 hdd solution is that for the price, you will get much much more space then a similarly priced ssd.
one benefit of going with an ssd solution is that the very latest and greatest ssds might beat out raid0 in a few tests. again, look at the numbers you research.
i personally have two vertex2 sataII in raid1 for redundancy. before them i had two WD Caviar Blacks in raid1. There is a noticible improvement in overall speed in this situation however if i had 10k/15k drives in raid0 instead i doubt i would have noticed as much without testing.
the ONLY place the Sandforce controlled SSD will be slower is in writing incompressible data. Otherwise I've had 6 HDD arrays and 1 SSD blows it away for an OS volume. An SSD can open and be ready to use 4 applications in the time it takes HDD to open 1.