Like fuzz, I have personal experience with both brands currently. I've been using a stinger SPV44 for almost four years now in a vehicle that had music for three of those four years...daily driven. No problems whatsoever with the stinger battery. Using an XS power D3100 in my other vehicle for about a year now and it's flawless. So like Sully mentioned earlier, go with whichever gives you a better warranty...
Never used xs batteries but all reviews were positive...... however used the stinger spv70 for almost 5 years now....... transfered from music application to engine bay and now back to music and absolutely no problems