Glass beds are better because they are flatter! I use a glass bed but clamp a 1mm thick piece of Tufnol (garalite ) to it as the actual print surface and use that for all the materials I use except Polypropylene for which I use adhesive polyprop tape (Sellotape) or 1mm polyprop sheet clamped on to the glass. Even with this set up PLA can sometimes need a coat of PVA glue.Even without the glass plate PVA glue might solve your problems with PLA ? Use a glue stick (Prit or Elmers) warm the glass to 40 or 50 C and apply it the glass.