Ok, Ed's gona climb up on his soapbox.
Each of these are entirely different animals, each with it's own characteristics and it's own +/-. A true hollow grind is two arcs, that start at the spine, and intersect at the edge.... this is a very sharp, thin edged grind, that excels at very fine cutting jobs. The drawback is that the edges on these knives are very delicate when compared to other types of grinds. All of that is assuming that the grind is actually a true hollow grind, and not what I refer to as a (I'll use the term "sorta" hollow grind.) By that I mean what many refer to as a "hollow grind" simply isn't..... these days we generally see a "hollow grind" where there is a slight hollow with a flat portion left towards the spine, with the "hollow" stopping short of the edge...leaving an overly thick edge that folks take down to some overly obtuse angle. This all started back in the late 60s/early 70s when a certain production knife company tried to correct an engineering/design mistake in one of their models....they had initially made the knife with a full flat grind, on a steel that was far too hard for that type of grind....people kept chipping out and/or breaking blades. But rather then rethink the steel, it's hardness, and geometry, they came up with this crazy grind that left the blade's edge super thick and heavy, in order to solve the issue of blades chipping/breaking. What they actually did was create a blade that's more closely related to a cold chisel then a knife. For whatever reason, this caught on with the custom knife world, and the rest is history. You can see this when you look at photos of some custom knives...... smallish hollows on the blade, and a HUGE edge bevel......all it equates to is "built in" cutting resistance. If you're going to do a hollow grind, do it for the right reasons, and with the intent to make it an attribute of the blade, and not just so it looks cool (which usually makes it a hindrance to blade performance). OK....off my soapbox now!
As far as ease, I personally don't have more difficulty with one then the other, however, I rarely ever hollow grind, unless its for a very specific purpose (small kitchen cutlery or razors). When it comes to a flat grind, I rarely do a full one of those either. The reason is that over the years I have studied/learned how to implement geometry into my blades that offer what I consider a good balance of reduced cutting resistance and strength. What I normally do is a combination of a flat grind on most of the blade, then convex the last 1/4" or less of the edge (depending on the blade type/use). Ultimately what I seek to achieve is using the flat grind to reduce weight, which makes a blade feel "faster" and "lighter" in the hand, and the convexed edge portion is there to reduce cutting resistance (I strive for as close to no edge bevels as possible) but because of the couple of extra thousandths in thickness just above the cutting edge, edge strength is increased fairly dramatically versus a full flat grind.
In the end, making something that look cool, but doesn't necessarily preform well, will sell you a few knives.....but people will quickly catch on, and you'll soon wonder why things started out so well, then fall off. If you make something that performs well, often times it will take a while for folks to discover it, but once they do, you generally have customers for the long term.