Depends so much on what your needs are.
Generally, because of the shape of the KLR tank, I very much prefer the teardrop shaped bags, as it seems they make better use of the available space there, and also prefer expandable bags so you can stuff a few things in there if you have to stop for auto parts or a couple beverages.
Magnetic mount bags are grerat for commuter duties, easy to reposition for refueling, and a medium sized bag (12L or expands to 15-20L) holds plenty in terms of tools, and ziplock with bailing-wire, zip ties, electrical tape, fuses, 6, 8, and 10mm nuts and bolts. Usually also have a small hand towel and/or handkerchief (use in winter to protect your face and in summer to protect your neck). I prefer one external rear-facing pocket for ear-plugs, chap-stick and Tums.
For dual-sport rides, or longer rides and week long trips to Moab, Death Valley or wherever, I prefer a larger bag, strap-mounted bag like the Wolfman Explorer. That bag is discontinued and replaced with a somewhat smaller Ranier. Virtually all of the Wolfman products are rugged and well made pieces of kit with lots of pockets for small parts and stuff, good availability of spare straps or map pockets. Have the strap-mounted Ranier now and its been good. Not sure if these are still made in USA, but they wear well and the mfr stands behind their product.
I am a fan of the Marsee brand, largely discontinued as well. Too bad 'cause these were as good as the Wolfman and also made in USA. My daily ride has a 12L Marsee with magnetic mount, and it works great on the commuter. Paid like $40 from a DR650 rider when I found it on craigslist. Since it was pretty cheap, I leave it on the bike full time and don't worry about the sun bleaching the fabric.
If I was looking to replace one today, I'd shop ebay/craigs/etsy for a used teardrop version of the Wolfman or Marsee, maybe Cortech or Joe Rocket if the price were right. Mostly 'cause I like those brands, and on account of me being cheap.
... all depends on your use.