Both are going to be strong balls that will work well on the fresh.  I don't have either one but I have some general observations with both.

The Lock is going to be more versatile overall than something such as the original Crux or even the Sinister.  It will push down the lane farther before reacting in the back.  It is more of a long/strong type ball but takes surface changes well and can be drilled to read earlier.  I also like the numbers with the new Rad-X core.

The Thug Corrupt is also one of the strongest balls available currently.  It's versatile and I like that Brunswick is using new composite covers.  They seem to be performing really well.  The Corrupt will give a bit more of a midlane read and may be slightly less angular than the Lock.  However, it is continuous just like the Lock will be.

I'll even make a third suggestion- the Track Paradox.  That ball is also very similar and it's one that I've really enjoyed using this season so far.  It's really versatile, skids nice through the front, reads the mids well and is probably one of the most continuous heavier oil balls I've seen in a long time.  I found that the cover also takes surface changes well and plays well with a variety of styles.

IMO, all 3 balls are very similar and you really can't go wrong with either one.  This is  one of those cases where I would work with your PSO to fine tune what will work best for you in making the final choice.

My team mate throws the Lock, and I throw a Paradox on a worn Anvil Lane THS.  Both were horrible in box condition, but both have been extremely good with high polish.  We both get plenty of hit even when chasing the oil in to 4th arrow with our low rev styles. 

Right now it's a $40 difference between the Lock ($169) and Thug Corrupt ($149) on buddiesproshop.com

All 3 should be a bit longer and be more angular in the back part of the lane.  From what I remember about the Mission X, it is a strong ball but reads the mids much earlier and tends to be heavier rolling compared to a continuous motion.  Any of the 3 would compliment it well.

The great thing about the new covers is that it doesn't matter as much anymore about using solids versus pearls/hybrids starting out on the fresh.  Covers have advanced a lot over the past few years and now you're finding pearl covers or hybrids that are as strong or stronger than their solid counterparts.  Also, you're now finding pearls/hybrids that can react very early in the mids and solid covers that are very angular.    For example, a few years back, I would have always used my Defiant starting out on the fresh.  Now, I can easily start with my Paradox and have something very similar.