TalesofWonder (TOW) and InStockTrades (IST) are the same company (technically so is DCBS).
They use (as far as I know) the same distribution center/warehouse - meaning whether you order from one website or the other, it comes from the same place, same stock of books, same packaging, etc...
Because of these last two DM sellouts, I just went ahead and pre-ordered Avengers v4 DM, Thanos Origins DM, and Spidey v4 DM. If your order is >$100 you get free shipping (vs. IST's free shipping at $50), but if you preorder, you can add a few more books to make it free.
They don't charge your Credit card until like a week before it ships or something. What I do, is bill it to my CC, and then over time, I work out with them to pay them via Paypal for the amount. You can 'make pre-payments' that way, if you're so inclined. Just email them first, obviously. they're great people. I've ordered from TOW for YEARS, until I realized IST was just as good and a teeny bit cheaper. But for DM covers, Avengers is $52 pre-ordered vs. $50 on release day at IST, but now I'm guaranteed the cover I want. You may not care, but for me, an extra $2 to ensure I get the cover I want is worth it.
Hope this helps you/others.
*p.s. I do NOT work for this company, I'm just a big supporter and fan!