Having played both a guitar for many, many years, and an arranger for many, many years, from my perspective, the guitar was much easier.
In both instances, I play the instrument and sing--that was the only similarity. It took a fair amount of talent and expertise to play the guitar, but the most difficult aspect of learning to play the guitar was learning to strum in various styles while singing.
The keyboard, which is a wonderful instrument in it's own right, takes care of the strumming part automatically, but, the on the fly technical aspects are far more complex than anything I ever encountered on a guitar. Not only do you have to remember the left hand chording, but additionally, you have to provide some right hand instrumentation for a host of instrument sounds, be able to rapidly select the proper sound (voice), sing the song, remember the lyrics, hit the correct fills, keep in time with the keyboard's regimented tempo, get set up for the next song, and dozens of other things I never think about because I just do them automatically.
It was a lot easier when I was a solo guitar player, sitting on a bar-stool with my 12-string guitar, a 100-watt amp next to the stool, a mic stand and a beat-up SM58. I had a lyrics book that consisted of a 3-inch-thick looseleaf binder that was perched on another bar-stool until I made enough money to buy a music stand with a weighted base. I played everything from old-time country to Malaguena, to House Of The Rising Sun, to 50 R&R. I was never a fantastic player, or even a great player. However, I was a good entertainer and that's what the bar and restaurant owners were paying me to do.
I listened to the posted song a couple times. To me it was played quite well--not fantastic. And, to me, it was boring as Hell. I sincerely believe Rory and Bill are much better guitar players. I'll stick with the arranger keyboard--for me, it's far more entertaining and much more challenging.