I am wondering if the swatch should be done in the round or flat. I've heard both opinions and since this is your pattern I'd like to know which you would prefer before I do my swatches. Thank you, I'm hoping this sweater won't be a failure ;/
As BrewCityMama says, it depends on whether you get the same gauge when you knit flat and when you knit in the round. If you don't know, then you should knit your swatch in the round to be sure you have a correct gauge.
One way to tell is to look at the wrong side of a Stockinette stitch swatch and see if there are slight "gutters" between every other row. If so, that indicates that your stitches are not the same size when you knit and purl. On the right side you may also see every other row is larger, but that is usually harder for people to detect than the gutters on the back.
The surest way to find out is to knit a swatch in the round and another one flat and compare the gauges. Once you do this, you will know whether you need to knit your swatches in the round or if you can get away with knitting them flat even if the sweater is worked in the round.
If you have to knit a swatch in the round, it would naturally have to be a larger swatch to complete the circle. One way to avoid that is to cast on your stitches on a circular needle for about 5 or 6 inches. Knit those stitches and then instead of turning the work, push all the stitches across to the other needle. Then leaving a long loose strand behind the work, knit another row. Repeat that for several inches and then you have your swatch made up of all knit stitches. You may want to clip all the loose strands so they don't distort the work when you are taking measurements. And definitely do not include any of the loose stitches at the edges in your measurement.
Don't forget to block your swatch before you take measurements since blocking can change the gauge.