Well I've had the chance to try both of these since I posted last week (Hotpot in freezing weather FTW)
Haha my brief take on these competitors who just so happen to be 2min walk from each other is that:
Soup Base: Cattle - just packs more flavour, especially the Tong Yum Gong!
Freshness: Lamb - hands down, all their meat & seafood are very fresh plus the balls like beef and fish are freshly prepared, never frozen, you can taste the difference!
Atmosphere: Lamb - It's much cleaner and just overall has a higher class vibe to it whereas cattle reminds me of a "Dai Pai Dong" in HK
Variety: Cattle - This is just from my personal experience, mind you, but when I went to Lamb they were sold out of quite a few things, especially my hotpot must-eats like Bo Choy and Deep Fried Fish Skin! .. so they lose some marks here plus I think Cattle has a few more things on their menu.
Price: Cattle - .. well they are both AYCE for the same price but for drinks, Kokanee for $3.50? Score! .. also Lamb charges $5 for a pitcher of plum juice but Cattle charges $1.50 for a jug. They put ice in the pitcher too whereas the jugs are chilled, so 1 pitcher is probably equivalent to about 1.5 jug, you do the math
Lamb offers $1 unlimited coke cans, Cattle is $1 for 2 coke cans, which isn't too important to me since I don't drink pop but even if I did I would assume 2 cans is more than enough for 1 meal!.. wouldn't want to fill up on pop when there's so much AYCE seafood waiting to go into your belly!
Service: Lamb - The lady (manager?) that was serving us was very nice, was very prompt to keep our soup and tea topped up, always asking us to change plates and even offered a little bit of friendly chatter, rare in these places. At Cattle all the staff looked like they REALLY didn't want to be there, had to ask for everything before they would bring it to us, from tea to napkins to new plates to soup!...and pretty much the only thing they were prompt about was our 2 hour seating limit and at 1h 40m they were harrassing us to pay up ... BUT to be fair: I went to Cattle at 7pm on Sunday and it was pretty busy and I went to Lamb at 12am midnight the following Sunday and there were only 2-3 other tables. So if the roles were reversed I wouldn't know how the service might have differed.
Overall I think they are both good in their owns ways, but since I've been to both in the last 10 days, if I had to go again next week I would personally choose to go Lamb again for the fresher food and hopefully they will have my things back in stock!