For 128 and 1TB sizes, no contest, I agree with Samsung being better. Write performance of 850 PRO totally beats the Budget MX100 to death, and I'd gladly pay $160 extra for 7 years of extended warranty on a 1TB SSD.
However, due to my needs (I game, and I tend to store games with long loading times onto SSD's whenever possible, although 'long' here is subjective), I value capacity higher than reliability, since I know I won't be storing important data on those SSD's, so it won't hurt if several years down the line they die, I have gotten my value out of them.
If I were to use the SSDs to store data of any kind of importance (such as backups), or if I need the durability (such as for a system drive) 850 Pro would be my choice, easily. The 10 year warranty is too difficult to pass up, not by the warranty itself, but as a measure of their level of confidence in their SSD life.