The triple will give you richer shots for the same volume of extraction, but while your own palate is the ultimate test one shouldnt normally need 25g of coffee to get a decent 25ml espresso. A double basket is often sufficient. The straight walls of the triple make it easier to get a tamper that is a good fit at the top and can go deep into the basket, but generally a tamper only needs to go about 8-9mm deep so any curve below that, providing its gentle, doesnt affect things too much.
Ive not seen a VBM basket recently; we have sold many Synesso baskets for VBMs and other machines with excellent reported results, however one user (perhaps GregWormald IIRC, apologies if Im wrong) said he got better results from the stock baskets than the Synesso. Bottom line? Chances are that either basket will do the job, given good peripherals (technique, fresh beans, good grinder etc). The main benefit of the Synesso baskets in your case is the convenience of not being basket-less while waiting for the tamper to be made. Of course the basket itself is excellent and has vertical walls rather than very slightly curved, but as your existing baskets arent real bad the difference isnt going to be as great as compared to say a Rancilio double. If youre looking to save a few dollars and dont mind being without your baskets for a week or two then send them in. Otherwise the Synesso option is definitely the go.
I dont have any experience with the EM0480 grinder in the VBM but if youre having difficulties with your shots I would be thinking that may be holding you back. Its a pretty cheap grinder to be using on a $2k machine; youd really be better looking at something like a Compak K3 or better.