I think the best information can be found here at Reef Central, because it's based on experience of people who actually have gigantea, haddoni, and magnifica. I've looked for information on websites, and most are horribly inaccurate, and many contain images that are of mis-IDed anemones.
In terms of threads, just skim through this particular forum (including the stickies) and you'll find a lot of useful information.
With regard to being the easiest, haddoni are the most common and ship farely well, so acclimation can be somewhat easy. IME, the exception are red haddoni, which appear to be horrible shippers (it could be the location in which they are found, transport time, and handling) but I've had two and was unsuccessful in acclimating them (however both were in bad shape when I received them and never responded to treatment -- more on treatment to follow).
Mags and gigs are horrible shippers, so only those people with experience can tell the difference between a healthy one and a sick one. If you choose to purchase a mag or gig, definitely read the sticky that discusses treatment with Cipro. Carefully review the photos people have posted so you can differentiate between the stages of sickness and acclimation.