Sunsweet
I've not used the PIS before so cannot comment, but i used the Swing. So far, I've used the following and these are my comments:
Medela Swing
Very good, but it's only a single pump. I used it for 8 mths. It's light and portable. Motor is not noisy. But there's a tendency to have milk backflow into the tube. I think that's the reason why my motor broke down halfway. When I went to the service center then I learnt that it's because of the position of the valve. So got to bear that in mind when using.
Avent manual pump
Got this pump as my Medela Swing broke down. It's tiring to use but it's very comfy due to the petals. Personally, I feel i get more milk as a result using this pump. I did consider to get the duo pump this time but it's too bulky and very heavy. I ever shared a nursing room with a mummy who used it. She gets letdown very fast but the downside according to her is she spent too much time fixing up the equipment each time she needs to pump and it's heavy n bulky to carry around.
Ameda
I've got a 2nd hand one from the forum. During the 1st few pumps, i feel it's quite good n fast in expressing milk. But it's a little less comfy than the swing. Somehow, I don't know if it's because the motor is not working well or whatever reason, my supply seems to drop a lot. I find the motor very loud and noisy. That's why i said I don't know if motor is not working well or it really doesn't work on me.
Am considering PIS or try Ameda again. THought of sending the Ameda to service and try again before investing in PIS. Undecided yet. Drop off Avent Duo from my wish list as it's really bulky though it's really comfortable.
On warranty... the warranty for Medela is supposedly to start when we purchase. But I spoke to their service sales staff. They said we can send in the warranty card after we deliver together with the child's birth cert and they will honour from DOB. I didn't know abt this. When I bought the Swing, I sent in the warranty directly. When I brought my pump to service, i showed them my child's birth cert n they honour the warranty period tho based on receipt, it shd hv expired.