No compatability issues. Out of the box the two sticks of RAM, 90% of the time (dependent on your mobo) will run at the exact same settings (the timings on the premium might be a bit tighter but whoopee). The reason the HyperXs are more expensive is because they
can be overclocked -- note that this does not mean they
are overclocked -- you have to do the OCing to get them to run them faster than, say PC3200.
Now if you are comparing say PC3200 Value and PC3200 HyperX then the difference is (a) the HyperX probably comes with a heatspreader and the value doesnt (not that you need one at such low clocks -- its only running 200Mhz/400DDR) and (b) the timings might be a bit tighter (so that you can OC it if you chose to). Its not something to throw your wallet into unless you seriouly want/can do some OCing