It's hard to say, but simply looking at prices - NEBL is around $4-5 and SUB is currently like $.125 - so, if you looked at potential for gain I believe SUB would have a better potential for a gain along with their launch at the end of 2017. Not sure, I am reading more on SUB's whitepaper at the moment, but both of these projects really interest me.
Dude that's not how the market works.
The price of a coin means absolutely nothing if you don't correlate it with the circulating supply.
The aggregate of the two is called the market cap. This is what you look at to know the valuation of a project.
So right now Substratum's market cap is twice as high as Neblio's ($80M vs $40M), which means that more money is in SUB than in NEBL rn).