I decided against going through extra security to go to the Welcome lounge this trip and instead went to the Z Sen lounge. The showers at the SEN lounge are a bit smaller and I seem to remember more amenities in the Welcome lounge (SEN has shower gel only). There was also a short wait for a shower in the SEN lounge, and I have never waited for a shower at the Welcome lounge.
As for the breakfast question - in my case, I got to the SEN lounge at 11:00 and they were changing over from breakfast to lunch, so if you want a late breakfast, definitely go to the Welcome lounge.