Smartwatch+, (modified) inverted and including weeknumber.
Smartwatch Pro (modified) with larger text and showing weeknumber.
I have been using Smartwatch Pro as the screen real estate is used to show calendar events and time, while the Smartwatch+ app uses screen real estate to also show current weather. As I use the Danish weather service on the iPhone to check coming weather forecasts (rather than current weather) I have been using Smartwatch Pro. If Smartwatch+ would show accurate weather forecasts instead, I would consider using Smartwatch+ again as forecast on the wrist would be very convenient.
Otherwise both apps are superb, and apart from the above points I would have a hard time choosing. Both are being upgraded to SDK2, and I suggest supporting both developers by buying their apps and trying them out - I often alternate!