In your case, I would recommend an iMac and and iPad. Not sure what your budget is, but I think you would benefit from having a desktop at home to do most of your tasks, and an iPad to be portable and do some tasks on the go.
The iMac gives you the bigger, nicer screen and performance, and the iPad gives you the portability. I have a MacBook Air and an iPad (two iPads actually), but I also have a Thunderbolt display for when I need a bigger screen. I found the performance of the i7 2013 MBA to be excellent for the apps and games I run. Truth be told I don't NEED an MBA, as I don't take it out at all. When I am out and about, all I need is access to email, a browser, and maybe maps. The iPad rMini is PERFECT for that. When I get home, I could make do with an iMac, but I had already bough an MBA (I am a former Windows users and have a dozen PCs around the house, newest one being 5 years old), and I am running Parallels on my MBA so I can run Windows on it.
There is no "perfect" answer. Different combinations will give you similar results. But if you do not take your laptop out a lot and you dont need that flexibility, a desktop may be a better choice. What is your budget?