Wow, that's kind of like asking boxers or briefs....
There are many great systems out there and each has its good points and bad. The hard thing to do is make a recommendation to someone who may have differing preferences. If he is happy with the system he is currently running with, then get one that is close to that. Though, he may be looking for a change.
I can make a quick review of the two belts, though I have not used either of these exact products
The iFitness belt looks like a great design. It is race ready with a small pouch, two bottles, loops for gels and toggles for the race bib. iFitness has a great reputation with their pouches and helped create a new niche market for small fanny packs. The 16 oz capacity of the bottles is typical of a 2 bottle rig. The negatives of this style bottle are that they do not accept ice cubes. You can work around this by freezing the bottle while half full then filling just before the run with cool liquid. The slant of the bottles is an improvement from the competitors who place their bottles upright. iFitness has a good reputation for quality.
The Nathan Speed 2 is a similar rig, though has fewer bells and whistles. It does not come with the bib toggles or gel loops. Note that if he is not a gel user, the gel loops are not important. The bottles are 10 oz giving the runner a 20 oz capacity on the run. Nathans expertise came from hydration systems; improving designs above long time players such as CamelBack. The molded holsters in this rig are a great add as reinserting a flask on the run is difficult in many systems.
Of these two rigs, the iFitness belt is the choice I wold make due to its ability to go from training run to race. Again, I have not used either product but iFitness is the new kid on the block with the fresh ideas.