union stream vs multiple operators

[Alexey Trenikhun]

Hello,
I have two Kafka topics ("A" and "B") which provide similar structure wise data 
but with different load pattern, for example hundreds records per second  in 
first topic while 10 records per second in second topic. Events processed using 
same algorithm and output in common sink, currently my pipeline is something 
like:

Source A->T-\
                       -> Sink
Source B->T-/

Instead of this pipeline I can union two streams and send them to common 
KeyedProcessFunction T:

Source A-\
                 (union)-> T -> Sink
Source B-/

What are pros and cons of these approaches?

Thanks,
Alexey