Proceed with caution, I'd say. Maazel does polarize opinion and this Vienna set is undeniably uneven. It is quite old now (and No. 1 in particular is starting to sound its age, technically). Reviewers have consistently praised 1, 2, 4 and 7, complained about the tempi in 5 and - rightly - absolutely written off 3 and (especially) 6. I myself find plenty of freshness in the music-making, much more than in Maazel's overstuffed and underinspired Pittsburgh remakes, but I certainly wouldn't want this as my only set. The Fifth is in my view one of the more effective of the set, but it is very fast.
Vänskä will give you a far more authentic Sibelius, with more consistent rewards.