Which is the best weapon?

Such a question is an open invitation to religious warfare.
Everybody loves to participate, but nothing is ever settled.

If the question means "what kind of fencing is the most fun?" then
the answer is: it depends what aspects of fencing you enjoy the most.
If you are fascinated by technique, bladework, and tactics, you will
probably get a lot of satisfaction from foil fencing.  More visceral
fencers who want to experience the adrenaline rush of a fast,
agressive sword fight will want to try some sabre.  Most epee fencers
consider themselves practical, no-nonsense sword fighters who rely on
as few artificial rules as possible.  Enthusiasts of more medieval
combat styles, involving armour and heavy weapons, should consider
joining the SCA or a kendo dojo.

On the other hand, if the question means "which weapon is the most
deadly?"  the answer will depend on a lot of factors, not the least
of which are the skill of the combatants, the presence of armour, the
military and cultural context, and the rules of the fight (ie. is
this a street fight, a gentlemen's duel, or open field warfare?).
Most swords are highly optimized for performance in a specific
environment, and will not perform well outside it.  Comparing two
swords from completely different historical contexts is therefore
extremely difficult, if not downright silly.

Then again, perhaps the question means "which style of fencing is
the most realistic?"  It must be said that questions of realism have
little relevance to an activity that has almost no practical
application in the modern world other than sport and fitness.
Historically, however, epees have the closest resemblance (among FIE
weapons) to real duelling swords, and the rules closely parallel
those of actual duels (sometimes being fought to only a single
point).  Other martial arts with a high realism factor include
kenjutsu and some aspects of SCA fighting.