The 026 is the far better saw. I do not know anyone that would take a 290 for one. I have owed a lot of both types (310s mostly, but an 029 and a couple of 290s). I still have a pair of 026 saws. You cannot 'port' a clammy 290 much, whereas you can port the holy crap out of an 026 in 12 different ways. They will absolutely scream even with mild porting. Then put a large mount bar low profile/Picco B&C on it, and you will spank a low revving, vibration prone and bulky 290.
As others have said here, that is a later model 026 made in VA Beach with a carbide TH, plastic starter cover, larger AF and obviously fixed jet carb. If you port it in any way, you HAVE to put a tuneable Walbro 22 or 194 on it. O/w you will run it lean and burn it up in a hurry.
Now with that all said, I am going out to use my 026/260 hybrid saw to dice up a few pines that I dropped here the other day. Light and nimble, and a lot of fun to use.