I'd need to start with a couple of presumptions/givens:
1. You don't need to sell to get money for something else.
2. you have plenty of space.
3. No one else is forcing the decision in any way.
With those caveats, it comes down to a few simple questions.
1. How often do you run out of space cooking on your 26'er?
2. How often do you have to limit cooks due to space on the 26'er (decide that you'll cook the corn inside because there isn't enough room). (This might seem like a duplicate of the first question, but there is a small, but distinct difference).
3. How often do you have to do some real planning and maneuvering with the 26 during a cook?
4. How big of a PITA is any of the above ?
I have 2 RKs and a 26 MiniRk. I love my Mini, but if push came to shove (and all of the above constructs were true), it would be the first one to go. Yes, even though I'd still have a RK left if I got rid of one of them, I'd still rather have 2 of them than the MiniRK. But, I cook for 30+ people many times per year and often cook for 50+. Even when cooking for 6 or 8 people, I've had to juggle things on my MiniRk. That's not the case with the RK. hell, if I want, I can set up 4 or more different cooking zones. There's just soooo much space and versatility.
For example, I could dump a 1/2 full mini chimney at the 9 o'clock position and direct grill some corn, spin the grate and dump a full mini chimney into charcoal baskets at the 12:00 position and 4 bakers up on each side of the baskets (8 bakers total), dump another partial mini chimney at 3:00 to grill off zuchinni and squash. While all that's going on, I could fire a full large chimney up front at 6:00, throw on some chicken to get a nice sear, move the chicken to the middle of the RK to cook indirect then drop some Ribeyes on for direct heat grilling. Somewhere along the way, I could throw on 2 whole loaves of garlic bread wrapped in foil to get nice and toasty.
I could cook the same amount of food on my MiniRK, but I'd have to do it in stages, rotating things off the grill as they finished to make room for the next thing needing to be cooked. With the RK, I stagger things going onto it, but end up pulling just about everything off at the same time.
