From what I've seen review-wise, in the real world you won't notice a difference between the two (or any newish SSD for that matter). There is some concern about the long term reliability of the TLC NAND flash in the regular 840 vs the MLC in the pro but I haven't seen this actually quantified anywhere. The pro does have a longer warranty (5yrs vs 3yrs) but is also $50 more on Newegg.
This is the most complete review/comparison I've seen on the 840 (regular) series:
In essence, its a great budget buy and stacks up well vs the competition. It suffers in write time but that's not really what you buy an SSD for (at least for HTPC purposes). I'm looking for fast boot, fast prog load and low power consumption which the 840 excels at. Real world performance differences between all the drives tested were pretty negligible IMO.