When switching between today's SSDs, I don't believe you'll see any significant real world differences for the most part. Reliability, warranty, track record, preferred manufacturers all come into play a great deal more I believe.
The Samsung 840 Pro is one of the best available consumer SSD products and Samsung have had a great track record with their newer SSDs. Each component in the SSD is manufactured exclusively by Samsung; the NAND memory, the controller, the RAM cache. I'd say that gives them a pretty unique oversight and level of control over the product. It's basically a product you can't go wrong with, though it's true the 128GB model is at a slight disadvantage in terms of theoretical speed compared to the 256GB model, simply due to the NAND chip numbers if I recall correctly. You'd be unlucky to have a problem with these models, I haven't seen anything negative regarding reliability over their lifetime so far compared to the great reliability track record set by previous products.
I don't know much about Intel SSDs themselves but each component comes from a different source compared to the fully in house Samsung. It's my personal view that this is an overall disadvantage than engineers working with their own productions. Majority says you won't likely have a drive problem though. I would never take advertised speed as reality though, applying to nearly all advertised SSD drives in existence.
In the end, pick whichever unit you feel most comfortable with. Recent SSDs trade blows in many segments but for general consumers, this generally isn't too significant in the end or not so much for anyone. The 840 Pro might not be at the highest position in every synthetic test but it sits very evenly distributed and doesn't fall low. Very pleased owner of a 256GB Samsung 840 Pro here and I personally believe the Samsung 840 Pro lineup is very impressive and the choice to make
Hope some of the above was helpful in some ways for you.
EDIT: Small note regarding those AS-SSD benchmarks, I've always considered access time to be a more critical factor and in the end, the reason SSDs win so majorly over hard drives for us. I didn't realise the Samsung had that large a margin versus some.
EDIT 2: Also remember SSD benchmarks will vary notably depending on their own condition (e.g data written and how their internal garbage collection and TRIM handles it) and from the surrounding environment and its settings.Edited by CoD511 - 3/27/13 at 12:45am