A couple of friends completed ultras last weekend. Wasatch 100 “made Headlands Hundred seem like child’s play,” said one. Rio del Lago 100 had “endless stretches of sharp climbs and … crazy-steep, twisting steps carved by a demented carpenter,” wrote another.

Meanwhile, I caught myself trying to explain to a friend why I feel that an upcoming neighborhood 5K seems harder to me than a 50K. She looked at me as if I’m nuts. How could a race one-tenth the distance, on a paved and not-too-hilly road, be harder than a mountainous 50K? I tried to explain that I’m not in shape to run a 5K like I used to, so to regain that zip in my legs and get my body lean and mean to cover 3.1 miles in close to 19 minutes seems more challenging than covering 31 miles of trail in close to five hours. It’s all relative, I said, and an ambitious time goal can make running feel very difficult regardless of the distance and terrain.

As I’ve pondered running events and goals, I’ve wondered what makes one event “harder” or “tougher” than another, and is “harder” always “better”? In 2012, should I graduate to the 100K or even the 100M distance—which seems ridiculously, out-of-reach hard—or try instead to get as close as I can to a three-hour marathon? Those goals aren’t mutually exclusive, but each takes a special focus. Alternatively, I could focus on 50K trail runs—probably my favorite distance and type of event—and savor the challenge of running them as well as possible. What would feel most satisfying? Which carries more bragging rights—and to what degree is my pleasure dependent on bragging rights?

And how should the logistics of traveling to and from the race factor in when determining what’s more difficult or doable? When I profiled Monica Scholz about running 25 100′s in 2010, she said, “The running was not the hardest part—it was the traveling. The travel was horrible. A lot of time it was a relief to get to the starting line and just run.” (Read the full story here.)

I know these questions are rather trivial compared to more significant work and parenting issues that need my attention. And I expect there are healthy, happy runners out there, like my husband, who can’t relate to this discussion at all. He is Mr. Mellow when it comes to running, and his definition of a satisfying race has a lot more to do with the scenery and the people than the distance and his finishing time. When he looks at the map or the course description for an extremely difficult, long race, he inevitably says, “Why would I want to do that?!”

And yet, I find myself turning these questions over in my mind when I hear ultrarunners enthusiastically  describe events as “brutal,” “insane” and “a beast”—as if that’s a good thing. I catch their fever and want to sign up for an event as crazy as the Hardrock 100, which I got a taste of while pacing nearly 30 miles of it in July. Whoever designed that course missed no opportunity to make it as hard as possible. Switchbacks? Nah, go straight up! At one point I was crawling—literally on hands and knees—over a busted-up beaver dam, trying to ford a swollen stream that flowed through a tangle of willow thickets, thinking, “This can’t possibly be the way—we must’ve gone off course.” But then my eye spied an orange ribbon and I realized, My God, this really is the race course. This could be the hardest thing I’ve ever done.

Hardrock’s top male finishers struggle to finish around 24 hours, whereas the winners of the Western States 100 crack 16 hours. Does that mean Hardrock is roughly 33 percent harder than States? Not necessarily; one could argue that Western States is harder than Hardrock because the States frontrunners run in a pack, racing each other the whole friggin’ way. Hardrock is nicknamed “Hardwalk” because unless you’re Dakota Jones, it’s pretty much a 30-plus-hour high-altitude hike with some runnable stretches.

UltraRunning magazine editor Tia Bodington articulates these questions well in her editorial in the September 2011 issue. “Steeper is not necessarily better and certainly doesn’t equate to a ‘harder’ designation,” she writes. “Some of the hardest courses in the country are the ones where runners can actually run the entire race because the terrain doesn’t offer any excuses to walk.”

I’ve only done two 50-milers so far: the Dick Collins Firetrails and American River. American River has a reputation as the easier one, because the first half follows a flat, paved bike path. To me, however, that bike path could make AR50 harder because the potential exists to run the first half like a road marathon and set a 50-mile PR.

I haven’t made up my mind about which events to train for in the coming year. I only know that I derive pleasure from the challenge that training for races presents—that is, from the methodical process of building up to reach a goal, and from the thrill of competing with others and with myself to set new PRs. But what kind of challenge should it be?

You can help me figure this out by sharing in the comments below what’s the “hardest” race you’ve done and what made it so hard. Was there a relatively “easy” event that turned out to be one of the most difficult? What tough race is on your horizon—and what makes it “tough”?