You can get the Samsung 850 Pro 1 TB new for $400? If so, then that's a good deal. If used then I'd personally opt for the Samsung 850 EVO 1 TB for $369.99 from NewEgg (http://www.newegg.com/Product/Product.aspx?Item=9SIA2W02DV8168&cm_re=samsung_850_evo_1tb-_-20-147-374-_-Product).
In answer to your question, no, the 4 x 256 GB will be faster than the 2 x 1 TB. Here's is my question: Do you understand the pros/cons of RAID 0? If you have one drive in the RAID 0 array go down, then all your data is gone. If you're not familiar with RAID and you want a simple setup, then perhaps a single 1 TB drive might be best for you. If you want to proceed with a RAID setup, then I suggest that you read up on a little more. Also, what is your system's specs? What are you trying to archive with this RAID setup? Faster boot times? Faster gaming loading? I'd just hate to see you add a layer of complication and not achieve what your goals are here.
A few articles on the Samsung 850 EVO (not Pro):
Samsung 850 EVO 120GB and 500GB RAID and RAPID Review - VNAND Goes TLC
http://www.pcper.com/reviews/Storage/Samsung-850-EVO-120GB-and-500GB-RAID-and-RAPID-Review-VNAND-Goes-TLC
Samsung 850 EVO and Pro 2TB SATA SSD Review - Multi-terabyte Consumer SSDs Are Here!
http://www.pcper.com/reviews/Storage/Samsung-850-EVO-and-Pro-2TB-SATA-SSD-Review-Multi-terabyte-Consumer-SSDs-Are-Here