I believe in free will (although I really don't understand what the distinction between free will and regular will is) mostly because I'd just rather it was this way. I'm not one to surrender power in any situation without good reason. I see no reason why the idea that I am in control of my future to a certain degree must be abandoned.
I understand that the current state of my being is the result of a vast, functionally unknowable chain of events. Each event in the chain was additionally the result of a vast, functionally unknowable chain of events. But it isn't every event in the chain that is unknowable. It is only the total. There are some factors beyond perception and beyond practicality to examine. However, this is not the case with all of the events in any chain.
Some events were conceived of intentionally, perpetrated by me intentionally and resulted in the intended results. Further, when these events were conceived of (prior to their manifestation in reality) parallel events were also conceived of and one event was selected intentionally for the perceived results of that event and steps to manifest the selected event were conceived and perpetrated.
Now, it is easy for anyone to say that whatever options I presented myself with were limited by reality and thus I couldn't freely choose any option I desired. I am willing to accept this. A lack of omnipotence does not equate to a lack of choice. This is still willpower to me, free or otherwise.
Additionally, it is easy to say that chain of events leading to the conception of these options determined which choice I would ultimately select and my intentions are only the illusion of intention. To this I say, the chain of events leading to the conception additionally consisted of many similar conceptions. Further, as I said before the chain of events is inexplicable. There is no suitable description of the chain of events. Thus, it is mostly speculative to suggest that the any event is the result of the past and only the past.
I understand that I am heavily influenced by my environment and my physical makeup. I am a product of nature and nurture. I am bound by physical reality. But these things are likewise influenced by me. I have modified my physical makeup intentionally. I have nurtured myself through trial and error. I have modified physical reality intentionally. These things bend to my will. To me, this suggests that my will is no illusion. My intentions create reality, they aren't created by it.
I firmly believe that the perceived future is what influences my decisions far more heavily than any preceding events or outside factors.