Here is a good article regarding the use of safety gear in sword training: http://marozzo.com/2014/05/18/training-with-minimal-gear/
Sonny always believed that training weapons should look as close to the real thing as possible, and also have the right balance in the hand (even if the weight was slightly off). He reasoned that one shouldn't build in bad habits with trainers that would be hurt you if transferred to the real thing. Same thing could be said for safety gear - whilst it keeps you safe in training, it should not build in bad habits that will hurt you when it is removed from the game.
We worked mostly with aluminum training blades, the positive outcome of which was to make us very accurate and precise in our targeting ... however, the down side was that we still had to train safely, so we avoided pokes to the face and hard strikes ... which are not uncommon in a 'real' fight, and certainly not something that should be left out of the toolbox ... So we also had padded trainers (though still all hand fabricated by Sonny to resemble swords in that they had an edge side and a flat side, and the balance was still in the right place) with which we could worry less about hurting our training partners.
These padded weapons meant that we could go harder and actually really tag targets ... though we still tended to avoid the face as we did not wear head gear as a rule - safety glasses, yes, but not masks. So an upside again ... but still a safety artifact, and the downside being that once these were in our hands for a while, we started getting careless and taking too many hit .... So back to the metal blades.
We also used sharps to get an even better motivation to evade and control our strikes, though the obvious down side to training with sharps is that we needed to be extra, super, careful .. which is good in one sense, but again, bad in another because now we are practicing to miss, essentially, and probably not fighting as aggressively as we should for fear of injuring our training partner .. or having them panic and injure us.
It's a tough balance to get rid of all the bad behaviors each type of training weapon brings ... but needs to be done to complete the picture.
Make sure to check out the comments, a guy called Tom Outwin wrote a really good one.
The guy who wrote the article is Ilkka Hartikainen, a fellow Finn, and if I ever make it back to my 'homeland' I will definitely go seek him out. The Marozzo system looks fascinating and Ilkka looks like a fun guy to free spar and play with.