Any specific reason you want to switch from the Bambino?
I have the Smith, it is very nice. I'd say ventilation is typical of all these aero helmets with visors - not great.
My only complaint about it is when in aero, I find it hard to see in front of me as the visor is a bit low, I find myself looking at the front rim of the helmet instead of through the visor.
I think my favorite aero helmet so far has been the POC Cerebel, although I found the back cover of the helmet was rubbing the back of my neck at times...
Sizing - Never tried a Bambino, but I wear a medium in POC, Specialized, Giro, and the Smith.

funny you ask, just did first ride today with mine. I have had it a few months but I have not raced since O-Side, where I used the Aerohead. It was a comfy ride, there was some whistling through the vents depending on head position. I did 2 4+ mi hill repeats in the mid 80 degree socal weather and while there was sweating, did was less hot than the Aerohead. The magnets are not as strong as the Giro...I liked being able to flip the Giro shield up on long climbs. The Smith holds the shield up if you're staying still but any quick moves or riding over a bump that lid is off the magnets.

The 2 things I didn't like with the Giro Aerohead was the perceived hotness and the size of the shield. I found it uncomfortable over my nose and made farmer blows post swim difficult. The Smith was better, though really molds around your (my) nose for a tight fit that was mostly comfortable.

I'm a Min most helmets and the M fit great on me. I can just get my ears in without issue and the helmet feels secure with minimal bounce.

I've had mine for a few months now and have raced with it 3 or 4 times already and used for a few training rides as well. Ventilation is alright, probably not a huge leap better than other TT helmets out there. I love the visor and Smith's proprietary Chroma Pop lens is really nice. The fit for me is perfect and it's very comfortable. I'm normally a medium and I'm a medium with the Podium as well.

I've noticed a few things. 1. I tend to loosen the adjustment at the back in T1 so that it slides onto my head easily after the swim. Then a couple clicks and it's back to fitting great. I found it hard to slide over the ears if it's already fitted to my head. 2. The nose piece on the visor should be more comfortable. I'm tempted to find some way to add some foam or something so that it doesn't hit the bridge of my nose as hard. 3. When you put your head down the wind can catch the Koroyd (honeycomb stuff) and whistle really loudly which scared the crap out of me at first. Now I think it's funny and serves as a reminder to get back into proper aero position!

The Bambino is too hot for me on anything longer than olympic. Want more venting. It's concerning to me that have a hard time seeing. I hold my head pretty low most of the time because of neck pain. Maybe I will look at something else. Thanks for the reply.

I should mention, a lot of helmets tend to sit a little low on my head, I guess I don't have a 'tall' noggin. For example, my road helmets, when wearing sunglasses with them, the bottom sides of the helmet tend to touch the arms of my glasses. So you may not have any issue with the height of the visor like i did.

Venting - yeah, as I and others mentioned, you are probably out of luck with most of these aero helmets... Maybe try the POC Cerebel - I found the visor on it maybe afforded a little more room in front of the face, and I never seemed to feel too hot in it. The Smith, and an LG P-09 I had, both felt really hot.

If you live in the US, most mail order houses offer pretty easy returns. Order a Cerebel and a Smith, try them on in aero on your trainer. If both are comfy to see out of, I'd go with Cerebel for possibly better venting.

I went from an old Giro Advantage 2 (long tail TT helmet) to the Podium this year. My Giro served me well for many years but it was time for a change.

I really enjoyed racing in the Podium. I thought the visibility was great - I really liked the lens system.

The helmet was much more comfortable that the Giro for me. It fit great and felt light (not sure of the weight). I went for the large as it was easier on my ears and the tightening system worked great.

Ventilation - I agree with others - none of these tt helmets are great here.

I hurt my neck last year and this helmet let me ride with a lower head position. As others mentioned, if you are going quickly and put your head right down your helmet will whistle at you quite loudly. Serves as a good warning to look forward!

I would definitely buy again.