1. The best philosophical argument for the existence of God is the ontological argument. It is the best, not only because there is something rather elegant about it, but primarily because - if it were valid - it would actually show that God exists with the degree of certainty which every theistic religion demands of its adherents. Sadly, there is no such thing as a valid ontological argument. If anyone tells you otherwise, I permit you to chide them gently. Try not to extend this into scoffing. Be nice.
2. I am increasingly convinced that probabilistic arguments for God's existence have, as well as their failings to persuade anyone as far as I can tell, the major failing that they are actually blasphemous. Let me put it this way: if Christian Theism is true, it is impossible that anything should exist on the supposition that Christian Theism were false. If we say of any thing, 'does this not make it more probable that God exists?', we are doing one of two things (or most likely both). Either we are moving God into the class of things which may or may not exist - a class which contains all things other than God already - and in so doing denying Christian Theism, or we are actually meaning something more like 'does this not make you feel more like God exists?', in which case we are appealing to subjectivity in a way which makes me uncomfortable.
3. If the existence of God is a philosophical question, not one of the Biblical authors ever thought to address the issue. Scripture is full of history; it is full of God proving himself in his words and deeds. It contains not a word of anything we might recognise as philosophy. I do not think Christians should be relying on a methodology which the Biblical witnesses, inspired by the ultimate Witness, saw fit to completely neglect. For us, it is history or bust; resurrection or atheism.
4. "Philosophical Theology" leads to Theism. Theism is not Christianity, or a relation of Christianity, or a stepping stone to Christianity.
5. "Philosophical Theology" generally wants to appear rational and sensible in conversation with the outside world. This desire may be well motivated in many, although I know that in my own period of chasing the no-god of natural theology that for some at least (i.e. me) the driving force is pride, and a desire to avoid the offence of the cross - which is foolishness to those who are perishing.