Celtic, that's incredible! Congrats on losing your 300 pounds!!!!!
At my heaviest, I was pushing 18 in regular sizes or 16-18 women's. One of the big differences that I remember was that the stomach was cut much more generously in women's shirts, with the larger thighs and waists in bottoms, so it really depends on your build. Do some trying on in the regular section and compare them to the W sizes and see what fits. It sounds like you'll be back in regular sizes again very soon, if you aren't already- it's a great feeling when you reach the point where everything at Lane Bryant is simply too big
Another thing you might appreciate- a friend who lost 90 lbs (size 18 to 4) told me once that the sizes get closer together as you lose weight and I've definitely found it to be true. Moving from the 230s to 200 lbs, I went from a tight 16 to a solid 14, but from 200 to 178 (where I am now), I went from that 14 to a 10 and I can see 8s on the horizon. It's pretty gratifying when drop another size after losing only 15 lbs or so!
Again, congrats and keep it up- you're definitely getting it done!