I don't have a warden and am pretty biased towards the LM. But, just from what I've seen in reading the forums, I think wardens generally have an easier time with solo challenges. By this, I don't mean the general landscape quests, but in challenges such as soloing 6-man content and the like. So, from that perspective, a warden might be the better bet.
To your question, LMs are at squishy low levels, but get sturdier as we level and gain more skills. Morover, one of the best things about the LM is that every few levels, you get new skills that make you feel like you have an entirely new class. Some may disagree, but I think the other classes (mini, burg, etc.), are still fun, but their changes feel more incremental.
That said, I would try both classes up until their 30s. LMs don't really start to have a good rhythm until then. You should have a pretty good feel for both classes and will probably gravitate towards one playstyle versus the other. Have fun, and happy hunting!