Don't know what PBM means, my sister has ghd and i have some random ones, the most important thing is to make sure they're ceramics, if yours already are there proabably isn't much difference. mine has a thermostat on it which means i can adjust it if i want dead straight or straightish, whereas the ghd ones don't have that. they're quite skinny too which makes it easier to manipulate the ahir. whatever you end up doing make sure you use a leave in conditioner or a heat protective spray to look after your hair and stop ot getting too overheated.
Well the brand itself doesn't matter. I personally use GHD straighteners myself, but as long as they are good quality ceramic straighteners, you should be alright. Having said that, my mother got some 'Nicky Clarke' ones and they are dreadful. They are too wide, the plastic handle gets very hot and there is a clasp which traps long hair and pulls it out... go for GHD!
i am had little experience with PBM myself, but i can tell you that GHD and any professional brand of straightener will be good. Personally i use GHD but brands such as KODO aare also exceptionall too. My advice would to be invest in a good pair (�90 - �120). Brands that are endorsed by apparent celebrity hairstylists such as Mark Hill or John Frieda to name but two, are often not as effective. Remember - always use a straightenening oil so not to damage the hair. Good Luck - i hope you find what you are looking for.
GHD's are miricle workers, ive had them for a while now anf there well worth the money, bit of advise though, get an iron spray, the GHD iron oil isnt that great the best one is KMS Flat Out, it smells gorge and leaves your hair really shiney and conditions it at the same time! So go for the GHD's