As mentioned before, check out the international partners that you can earn status miles on. If you fly a lot of international KLM may make NW the better choice.

If you fly primarily on NW, you won't get the 1000 mile online booking bonus if you're a OnePass member. Small point, but maybe important.

If you primarily a lot of short segments (which DFW-LIT certainly is), then it's easy - go with OnePass. LIT-MEM-DFW R/T is 2000 status miles in either program. It would take 12.5 round-trips to qualify for silver in Worldperks. However, since OnePass allows for segment qualification at 30 segments, you could get silver with 7.5 round-trips.

I flew 55K miles and 90 segments last year, about 70% on NW. I wouldn't have even come close to Platinum in Worldperks.