Best FF program for me?
 

I don't travel too often, but here's what I currently have:

Delta Silver (w/Amex Gold) - ~70k miles
United Premier - matched my Delta status - 0 miles (short 1600 mile RT coming up)
Emirates Silver - ~26k miles

I usually only fly to JFK-LAX for personal flights, and occasional domestic/international flights for business. Trying to figure out what the best option is for an upcoming flight, and what FF program to focus on.

I will be traveling for business soon, business class, same destination I received ~26k miles on Emirates a month ago. So I can either fly Emirates again, which will bump me to Gold, but I don't really have any use for Emirates miles from what I can see, and it looks like the partnership with United expired in May. Other option is to fly on an airline with a good FF program that I have use for domestically (delta, united, etc..).

Obviously I already have Delta miles, but I'm wondering if United (or another) is a better program and has better rewards - I've never booked a reward trip with Delta or used any miles I've accumulated... I just hear that it's not a great FF program for whatever reasons.

Also, I'd be up for opening a new credit card for a good promo offer (already did the Delta Amex Gold for 50k miles, and Capital One Venture for miles match).

So bottom line, should I:

1. Fly Emirates again, get Gold status, have around ~60k miles
2. Fly Delta, would stay at Silver since no other Delta flights yet this year
3. Fly another airline and start a new program, like United (already Premier).

Korean allows collection of Delta and Emirates miles. Combining those would max reward ability.