None of them?

Everybody has their preference for a reason but 140.6 is still never 'easy' ;-)

The PC answer is "none because they are all the same distance." But I know what you mean: Would a flat (Florida) one be 'easier' than a hilly one (Canada)? If you live and train in a flat area, then sure. But if you are lucky enough to train at elevation, going to Florida and hammering 100% in the saddle may suck. Is an ocean swim with a wetsuit 'easier' than a no-wet suit lake swim? Maybe. But then the waves and current may kill you. There are so many variables. Similar to what has been said before, the 'easiest' one is on a course and with a climate that is most similar to that which you have trained.

I agree with Anton that if you've done the training then the actual event just puts it all together and you just go out there and get it done.

What makes any outing at this distance hard or harder than another, I think, are the various conditions that you might be racing in. For example's sake let's consider just one IM in particular: Wisconsin. The conditions in 2006 with the choppy water, the dismal rain, and sub 40 degree air temps probably added several facets of difficulty. That same event in 2004 (or was it '05 ?--- can't recall for sure now) which had record humidity and heat which caused lots (more than usual) of folks to have to bail out and/or receive medical attention during or after the race had different degrees of difficulty based on those conditions.

Add to these general conditions how you feel when you toe the line that day, how you manage your nutrition that day, and whether or not freak things like broken chains, little kids running across your path on the bike, getting your nose broken by a strong kicker in the swim, or slipping on a banana peel through an aid station and you realize that the level of difficulty at any given event is just a fundamental element of the variables inherent in racing.

I goggled the OP question and I like the comment about the hardest one is the one that takes the longest to fill. At least that is an objective answer.

I agree with what others have said, each race will be harder or easier for you personally based on many variables. For instance, I sweat very little and overheat easily. The hardest race for me would be one where it is hot and humid. However, I'm a strong swimmer, so a "hard race" for someone else with a killer ocean swim is not going to faze me. In deciding which race to do, I think it's a good idea to think about what you want your experience to be like, how you like to challenge yourself, what kind of terrain you're interested in, and just possibly what kind of vacation you'd like to build around it (my family certainly didn't complain about going to Florida's beaches in November from the rainy Pacific Northwest.)

In any case, 140.6 is always going to be a challenge, and most likely there will be challenges on that day which you have not foreseen, from crashes or technical difficulties to injuries, overheating, or nutrition and hydration issues. Even experienced Iron-distance athletes sometimes have a race that falls apart when all should be going well. I also agree that if you're trained up for it, 140.6 is difficult, but very doable. It should be an exclamation point on your paragraph of training. I think many people enter the race either drastically undertrained or overtrained and fatigued. Striking that balance is, IMHO, more difficult than the race itself. I found the Ironman distance to be quite enjoyable (and that's not just the masochist speaking!)

Isn't the phrase "easy IM" an oxymoron? The distance was designed to be hard, regardless of venue. Besides, if you're looking for the easiest 140.6 you can find, then you may need to re-assess your triathlon goals - namely your target distance or training commitments. The obvious exceptions would be if you're (1) on the bubble and hoping to qualify for Kona, or (2) worried about finishing in 17hrs.

How about we consider the course records of each IM?

The same pros race all of 'em, so maybe Ironman Germany is the easiest since..
in
1997 - Luc Van Lierde broke the 8 hour mark (7:50:27). Oddly enough he did it in race conditions Scott Tinley called "the worst ever" with 30mph headwinds on the bike.

In 1996 - Luc Van Lierde set the Hawaii course record at 8:04:08

Using him as a measuring stick my vote goes to IM Germany.

I've heard many people say IM Lanzarote is the toughest.

PoC

is that the roth challenge (the old IM Germany) or the new IM Germany down in frankfurt (I Think)

A friend was telling me about an indie 140.6 race in Canada that is only for beginners and is flat as a pancake. I don't know the name of it but could probably find out if you can't find it or someone here doesn't know about it.

Not sure if it's the one your friend is talking about, but there's the Montreal Esprit tri. It's full Iron distance (and other distances).

The swim is in a rowing basin that's dead calm, the bike is on the completely flat and smooth F1 circuit, and the run goes around the rowing basin... completely flat.

jono