I would say Rush before Guardian definitely. The extra damage and distance from Rush would not only save you an extra hit here and there, but it'll also allow you to travel faster and make that % of xHKO significantly higher. Much better than saving pots.
Another perk of having higher leveled Rush is that it also activates much farther. With level 1 Rush, activation distance is just in front of the monster. However, with max Rush, activation distance can be about 3-4 Skelegons wide.
Also, Rush distance has been increased by 20 pixels as of current KMS patch.
I'm not a Hero, but from an analytical perspective...Rush vs. Enrage would be the more careful case to consider since Enrage boosts a great deal amount of damage to the Hero...enough to offset the extra damage from Rush (but not the walking distance and time saved), and can help quite a bit during bossing when not appling. If you think about it, with Enrage and Rage's new 12 atk feature, there is no more need for you to carry warrior elixirs anymore. Having an extra +14 atk every 4 minutes can definitely speed up training and bossing (as well as your EXP gained during bossing). MW 20 is overrated for Hero since Enrage's extra attack can offset most of the average damage boosts of MW 20 even in light of Enrage's cooldown - not to mention you'll probably be partying with another class who most likely already have MW20.
Guardian, on the other hand, merely saves you pots and success is inconsistent. If anything, Achilles would help overall survival and pots saved much better. During training, having a monster being stunned or not mostly serve to save pots, since the monster's attacks will not budge you significantly to slow you down with sufficient Power Stance. After all, Guardian's 15% activation rate at level 30, when combined in light of Stance 30's 90% no KB rate...only serves an extra 1.5% (no idea how Devil's Sunrise got 1.6% from 15% of 10%...) chance in ignoring KB effect - and thus a slight boost in DPS, as KatanaKiwi pointed out. Still, pretty wasteful of 30 SP I would say.
And, as mentioned by Phoenix already, if there is SI for 2h sword, then Guardian would be a complete waste. This is why I actually chose Monster Magnet over Guardian on my Paladin, since now I have the ability to go to mobs with Rush as well as pulling entire mobs to me (VERY helpful at weird maps like Skeles and ToT and can change the entire map cycling mechanism and overall efficiency). I think it's nicer to be flexible and have a more diverse arsenal of active skills that can be used at whatever situation than just to save pots at 15% rate. Anyway, Monster Magnet is another warrior controversy all by itself that I don't really want to get into right now.
To summarize - unless you plan to level solely by BF with apples, Rush or Enrage will be a wiser choice than Guardian. And Guardian is only preferred over Achilles when if even with Achilles, you still can't tank a hit from a specific boss.
In the end, even with all this analysis to help you decide what's better, it's still your choice. You don't have the make the "best" Hero in all situations - the Hero you like is the best Hero for you. =)
Another perk of having higher leveled Rush is that it also activates much farther. With level 1 Rush, activation distance is just in front of the monster. However, with max Rush, activation distance can be about 3-4 Skelegons wide.
Also, Rush distance has been increased by 20 pixels as of current KMS patch.
I'm not a Hero, but from an analytical perspective...Rush vs. Enrage would be the more careful case to consider since Enrage boosts a great deal amount of damage to the Hero...enough to offset the extra damage from Rush (but not the walking distance and time saved), and can help quite a bit during bossing when not appling. If you think about it, with Enrage and Rage's new 12 atk feature, there is no more need for you to carry warrior elixirs anymore. Having an extra +14 atk every 4 minutes can definitely speed up training and bossing (as well as your EXP gained during bossing). MW 20 is overrated for Hero since Enrage's extra attack can offset most of the average damage boosts of MW 20 even in light of Enrage's cooldown - not to mention you'll probably be partying with another class who most likely already have MW20.
Guardian, on the other hand, merely saves you pots and success is inconsistent. If anything, Achilles would help overall survival and pots saved much better. During training, having a monster being stunned or not mostly serve to save pots, since the monster's attacks will not budge you significantly to slow you down with sufficient Power Stance. After all, Guardian's 15% activation rate at level 30, when combined in light of Stance 30's 90% no KB rate...only serves an extra 1.5% (no idea how Devil's Sunrise got 1.6% from 15% of 10%...) chance in ignoring KB effect - and thus a slight boost in DPS, as KatanaKiwi pointed out. Still, pretty wasteful of 30 SP I would say.
And, as mentioned by Phoenix already, if there is SI for 2h sword, then Guardian would be a complete waste. This is why I actually chose Monster Magnet over Guardian on my Paladin, since now I have the ability to go to mobs with Rush as well as pulling entire mobs to me (VERY helpful at weird maps like Skeles and ToT and can change the entire map cycling mechanism and overall efficiency). I think it's nicer to be flexible and have a more diverse arsenal of active skills that can be used at whatever situation than just to save pots at 15% rate. Anyway, Monster Magnet is another warrior controversy all by itself that I don't really want to get into right now.
To summarize - unless you plan to level solely by BF with apples, Rush or Enrage will be a wiser choice than Guardian. And Guardian is only preferred over Achilles when if even with Achilles, you still can't tank a hit from a specific boss.
In the end, even with all this analysis to help you decide what's better, it's still your choice. You don't have the make the "best" Hero in all situations - the Hero you like is the best Hero for you. =)