On paper, the Makita BTD144 looks awesome....small, light weight, powerful, brushless motor, etc... However, if you go to Amazon and read the reviews about the Makita BL1830 batteries (that the 144 uses), there are many unfavorable reviews.
Dewalt explicitly states you will get 2000 charges out of their NANO LiOn batteries versus 500 for the BL 1830. If you search across the internet, you'll find the A123 batteries that Dewalt uses have great reviews. In my experience, batteries are the Achilles heel of any cordless tool and they always fail before the tool. I have two impact drivers now and the batteries are dead for both. The tools themselves work fine. However, the cost to replace the batteries is a significant percentage of the price to buy a new tool (with much better features).
I was ready to buy the 144 this morning. However, after reading the Amazon battery reviews, I'm now leaning toward the Dewalt. Of course, if you only use the tool occasionally, 500 charges may suit your needs. In which case the Makita is VERY nice.