Grain lines -
 

When possible, I prefer to have lengthwise straight of grain for the outside edges/borders of any quilts I make -

Because, usually, the lengthwise grain has less stretch and is more stable.

The down side of using the less stretch direction - it is more difficult to ease in any oversized blocks/pieces.

Ain’t that the truth!!

That's true, but I use the same method.

I almost always use WOF because it's easier to cut and I don't find a big difference when dealing with WOF or LOF for borders.

Borders are cut lengthwise. I don't piece border fabrics unless it is to add a cornerstone. I know...I know... supposedly you don't "see" the piecing on borders after they are quilted.

I so totally agree with you on this. I try to watch my fabric grain for the grain going lengthwise where ever possible.

I agree on the concept that LOF is the better option, for less stretch and stability ...
... plus eliminating seams.

However ... as an interesting segue,
... the only time I have had wavy borders was for my FWS quilt, when I was "smart" using LOF!!
And what a bear (no pun intended BearIsGray!:))they were to get flattened out.
I finally got them there, but it was not a good experience at all.
Yes, now, I only use WOF.

Of course, that will change someday when I choose a border print running LOF! :)

I use WOF as it is much more economical. I’ve never had the wavy border problem but I do measure and then clip on my border (using binding clips) carefully - match up the middle and quarter points.

I am a recent convert to LOF for borders. Now that I have had several years of quilting on a longarm, I am a happy camper when the borders are flat!! I am also ocd when it comes to patterns and the seams in the middle of a border really bother me :(. The LOF is a good solution for me. I measure the middle of the quilt and cut both sides of the border fabric to that measurement. bearisgray - you are correct however - if you have an oversize block it is harder to ease in. When that happens and it isn't too far off, I revert to my old sewing habits - remember easing is sleeves?? I will loosen the tension and run a quick stitch just inside the 1/4 inch mark - sometimes just the stitching alone is enough to pull in the fabric and make it fit.

I have never found any difference in lengthwise or crosswise when sewing borders. I have my border fabric stiff as paper before cutting and sewing. I never have a problem with floppy or wavy borders.