Ok...I think I have the conclusive answer finally. Math seemed like a legit way to come to a decision but I feel that only tells us who is stronger. Now...to win an arm wrestling contest, might I suggest we debate who is better able to go
OVER THE TOP!!!
Based on this question, I think I've come up with a clear cut, five point criteria on how to win at arm wrestling. I've evaluated both Havel and Tarkus on these five points:
1. An arm wrestler needs wrist flexibility.
Based on this criteria I've looked at their armor sets. Tarkus' armor has a clear design emphasis on allowing wrist movement. Havel....not so much. Now, this only applies to when they're wearing armor I admit which they might not wear for this matchup. However, since they're both custom armor sets, I think it's fair to say that they're designed based on what each warrior feels is important.
Winner- Tarkus
2. The ability to ram through things like a semi to confront the villain.
Both use bash techniques so this one seemed to be a close one at first. However, Havel is trapped behind two wooden doors that are possibly over 1,000 years old and does no bashing. Tarkus' shield specifically references it's ability to bash. Havel's shield actually kind of is "anti-bash" with what it does.
Winner- Tarkus, though I admit I'd actually like to see him ram through a few gates to call this conclusive
3. An estranged son that you try to reconnect with during a road trip.
The obvious answer is that Tarkus is a knight and Havel is a bishop. Suggesting that a man of the cloth might be more likely to have a vow of abstinence. I don't know enough about their religion to lean that way though so...
Winner- Tie, we just don't know enough about their religion
4. A rich, overbearing father-in-law to start a custody battle with you.
This is another tough one. A knight could just as easily be part of the nobility than a bishop and therefore have an a-hole rich father in law.
Winner- Tie
5. A blue collar work ethic, with a heart of gold hidden deep within.
Let's start with the heart of gold. Havel's items indicate he held a lot of hatred inside and tries to smash you on sight. Tarkus is not only helpful, he's willing to do all the work. Even on NG+++ where I summoned him just to see if he can hold his own still (the answer is, oh hell yes). As for the blue collar work ethic, I just assumed that the Iron is "Black Iron" from his proximity to semi smokestacks.
Winner- Tarkus
That's two ties and three to Tarkus. Sorry Havel fans, evidence suggests that Tarkus is more similar to Lincoln Hawk than Havel is.
- Spoiler:
A big "Thank You" to anyone who suffered through my overly long and complex joke regarding the easily forgettable yet somehow epic Sylvester Stallone movie.