I'd take the 5 for $200 ea. I'm running out of room, and need plants mature enough to survive our sizzling, torcherous summers in Phoneix. When trimming fronds my larger plants often damage smaller underplantings. 15 gal or larger size plants are probably kept outdoors, therefore being more acculmated to ground planting. They make for instant visual impact. I also have a bad track record keeping smaller potted plants alive. That said, I do agree with what others have said about smaller planting establishing quicker than plants the next size up. I planted a S. Palmetto 24" box, opposite a 15gal S. Blackburniana. The 15gal has doubled the size of the 24" box dispite it being in the ground a year earlier, recieving more sun and water. Now, is one species (Blackburniana) faster growing than the other (Palmetto)? I'm not sure about that.