No no no. You're so half-right that you're wrong.
RAID 5 can allow reads from all spindles simultaneously
So does RAID 0.
3 spindles in RAID 5 will have better performance of two in RAID 0
Not true. At most you get the same performance since only 2 spindles are used to hold data while the third holds a error-correcting check. You generally get slightly worse on reads because of the overhead of the calculations for the third drive. Writes to a RAID 5 are almost always slower since you have to generate the error-correction, so it depends on your controller. Add-in controllers are faster than built-in motherboard controllers.
Depending on the brand and quality of your RAID controller, RAID 5 should be noticably faster than RAID 0
No it won't. If you have RAID 0 all drives are used for data so you get about the number of drives times the speed of a single drive; but for RAID 5 you get the number of drives
minus one times the speed of a single drive, so reads are slower for the same number of drives. Also writes are significantly slower, depending on the controller because the controller has to create the extra drive's correction codes.
If gaming speed is your only concern, stick with RAID 0. However, multiple drives mean that one drive failure out of the set will cause the whole array to fail. For example, if you have a 1% chance of failure per drive, four drives in RAID 0 will give you 99%^4 chance of no failure = almost 4% chance of failure instead of 1%. However, with four drives in RAID 5 you need two drives to fail, meaning that your chance of failure means about 1/100 of 1% (= 0.0001) of simultaneous failure times 6 ways to fail means 99.99%^6 or about a .06% chance of loss of the whole array. .06% vs 4% means a factor of 67 difference in reliability in this case for RAID 5 vs RAID 0.
So I'd say, if you have only 2 drives in RAID 0, and you use the RAID only for non-critical data, your drive setup is probably okay. If you're using more drives, consider RAID 5. You won't get the maximum speed, but you won't lose everything to a single crashed hard drive.
--dv