I have a standard P&T and loved it. When then toddler is on the top it is only for such a short time before you need to put the toddler seat on the back where you then need to put the smaller child in it so there shouldn't be a problem with heads hitting bars. My ds was in the rear seat for ages before my older DS decided he was too big for a pram. I do have to say though I am a pram addict and I have just bought myself a new mountain buggy LOL only because I don't need a double anymore.

I would def reccomend the vibe though I have heard such good things about it.