Like many on SF I prefer traditional suspenders/braces for suit trousers, belts for odd jacket/trouser combinations.
My ideal suit trousers would have DAK adjusters, suspender buttons, and no belt loops.
Just to chime in, for me, 100% on side adjusters. I don't wear belts, other than with jeans or certain casual wear. With suits, I wear suspenders or just 'nude' so I strongly prefer side adjusters for a cleaner look.
As for the fabric, I have to say I've been waiting for S&P to offer the full canvas suits as I'm going to purchase some staple suits in the next year. Put bluntly, I'll likely end up at Suit Supply, because of the Italian fabrics. I have no experience with this Chinese fabric, but to me, I am extremely skeptical it's almost as good. I'll pay $100 extra for the premium fabric, since I'm already paying a premium for full canvassing.
I just don't buy this idea that an Asian milled fabric may not be a premium fabric. Maybe it's just the industry I'm coming from but I don't buy into the "Well this is how it's been done so we should stick with it" mentality, and I don't like the immediately negative perceptions toward Asian manufacturing as we're not talking about Old Navy or Banana Republic, so I trust Spier to choose an appropriate fabric and I'll buy regardless of the decision. At >$500 though I will have to start considering Benjamin (eHaberdasher) as well.
I'm in favor of side tabs + suspender buttons.