If you can swing the $ go for it. There's no way around the fact the M3 will be more expensive all around but if you can pay to play why not. You only live once so get what you want.
Given your low mileage and (apparent) desire to switch cars often, consider taking over someone else's M3 lease instead. In particular, go for the ones that have put down multiple security deposits to buy down the money factor but are desperate to get out of the lease and will allow you to keep the MSD at least end.
EDIT: you should look into a CPO 996 TT. A friend got one for low $40s recently. Great deal and 600hp is just $3k in mods away!