The battery life of the Opus 200 is pretty much comparable to the SX Mini, both will last you a day with regular use. If you use high power on either, batteries will run out quicker. However, only with the SX Mini can you swap batteries, the Opus needs to be plugged into a charger. YiHi has also added support for Titanium and could add support for stainless steel in the future.
And you can program custom TCRs for any material that would work for a TC coil into the DNA200 and account for other variables other than the wire itself, but I'll give you the ability to switch batteries.