The UDC20 has a cooling fan too but it's around the side.
The new UDC30 supports the LiFe type battery, the including charging leads are supplied with Deans connectors for connecting your required lead up instead of the old DC-in style connector. Optional 12V input is a separate lead too meaning the charger is more compact for storage. There's also a LiPo fast charge mode on it too.
When the UDC30 was released the RRP was lower than the 20 I think or roughly the same price. It's a no brainer, go for the UDC30.
__________________
|