@Deerber:
RM gives speed debuff (which is quite significant - phantoms, dragoons, abombs becomes so much easier to shoot), slightly higher damage debuff. It can lock down spawns and even provides wall hax. It's stagger potential is insane - PM can't stagger bosses, RM detonation can. As for synergy with TC, RM has an advantage over PM because it's biggest disadvantage (long recharge speed) is nullified.
The 3 sec. arming time is not that big a deal. Because of it's 12m debuff radius, you don't have to plant it right next to the enemy. Put somewhere predicting the enemy movement.
Also, I made a typo in my prev. comment. I mean to say recon mine is a better power (on the whole) - not a debuff. I'm not saying RM is miles better but it is slightly ahead of PM as a power.
The hunter mode is the key difference between the two characters.
Speed debuff - really? It might be slightly useful if you're sniping, alright, but with a spread weapon like a Talon it's next to useless 
Slightly higher damage debuff - yeah sure, we all agree on that I guess.
Lock down spawns? What do you mean, exactly? XD
Wall hax - again, only useful if you're sniping, otherwise you've got your scanner/HM that does the same job.
Staggering bosses? Are you serious? Who the hell cares about staggering bosses?
It might be the single most useless attribute a power can have in this game... Especially on a kit that's gonna stagger them (and therefore lock them out of other staggers for a gazillion seconds) in like... 2 Hits?
And no, it does not have an advantage over PM in synergy with TC. At all. Sure, its cooldown is lowered to 3 secs, but the 3 secs activation time isn't. Having 3 secs of downtime on 12 secs of cooldown is one thing, but having 3 secs on 3 secs of CD is a whole other story.
And yes, the 3 secs arming time IS a very, very big deal. I know it has a big radius and I know I can predict enemy spawns and place it the right way, but this doesn't change the fact that whenever I place it, it takes 3 full bloody seconds for the debuff to become active (let alone the chance to stagger and damage things). If I don't shoot during these 3 secs, I'm losing so long of a time that I won't ever be able to keep up with a GI. If I'm shooting withing those 3 secs, I'm getting no debuff and therefore I'm never gonna keep up with a GI and the advantage it'll get in those 3 secs.
I do agree that, if you take the powers alone, RM is better than PM. Actually a fair bit better. But sadly, in this game, powers change face completely when coupled with TC - and so does the relative strenght of them. If I have a CD of 12 secs, having to wait 3 secs for my debuff to become active isn't that big of a deal, as I'm not going to use the power very often anyway, so I'll just place it somewhere, and keep it there for most of the wave. However, as soon as my CD becomes 3 ish seconds, things change. Suddenly, I'm able to spam the power pretty much as I want. But now, having to wait 3 secs for it to arm becomes veeery crippling. Furthermore, you have to choose whether you want it to debuff, or to provide CC and damage. If you choose CC and damage, *every* time you choose CC and damage, you need to wait 3 full, bloody seconds to get the debuff to work again. With PM you just get everything in a nice package that you get to use every 3 secs. You don't have to choose, you don't have to wait. It's right there when you need it.
RM might be better if you use a semi-camping playstyle, like maybe you guys do in solos (Loufi got me thinking with his post, it might be the reason for our difference in points of view), but as soon as you have to move all around the map killing things as fast as possible like you do in a team game, PM just becomes flat out better.