I use both. The magnaglide classic is MUCH more cost effective but only come in a few colors. Also because it is a finer thread it goes further per bobbin load. The delights will match your top thread exactly but not all Glide colors come in prewound magna glide bobbins. I tend to use the delights, which are only sold in the jars of 10 for the size bobbin we need, only when I want to showcase the back of the quilt, like this one:
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On this quilt I used delights and in some of the colors I wound my own. I use the delights if I need my bobbin to match exactly (which is rare).
If the backing fabric is very busy and the quilting won't show, or if I am not trying to make a visual impact on the back, then I tend to go with a magnaglide classic in one of the colors that comes closest in value to what I have in the top.
Additionally, if I am using a finer thread on top like invisfil or silk then I will go for the lighter weight magnaglide classic or Superior Bottom line but I much, much MUCH prefer the magnaglides. Superbobs tend to have poor tension/tension changes in their cardboard prewounds when you go through the first 2/3 to 3/4 of the bobbin. Not sure why that is but many LA quilters have noticed it. We save those partial prewounds for hand sewing the binding or pass them on to the client so they can.
Last edited by feline fanatic; 07-02-2015 at 08:39 AM.