You have very large libraries for both iTunes and iPhoto that you must need the space? Because these 2 you listed are both dual drive enclosures, RAID capable. And if you setup RAID0 with these you are running some extra risk in HD failure also, which means a more solid backup is also needed, so extra cost is there.
I myself have a 3+3TB WD Thunderbolt Duo, it is not the fastest as you can see from all the benchmark reviews, but it is quiet (no fans), affordable, at software RAID 0 is giving 280-300 read write in blackmagic test which IMO is good enough for general use. The LaCie is at a more robust class, more suited to professional use.