I researched a lot of bags but the "it luggage" brand came up time and time again for best value:weight ratio (and often simply the lightest weight). I bought my first suitcase from the brand at Primark for 50 euro. I bought a second one ("Stiched Squares" style) from ebags for 75 dollars. You'll notice that the MSRP many online sites list for the brand is far more expensive than what the bags actually sell for, so definitely do some price comparison.
Style: The Lite
Purchased from: Primark
Exterior dimensions: 30.3"x18.3"x10.4" (77 x 46.5 x 26.5cm)
Linear dimesion: 59" (150cm)
Weight: 4 lbs, 10oz (2.1kg)
Pros: Very light, handles and fabric held up well.
Cons: Wheels often get stuck with lots of weight (23kg), extendable handle fell apart (but was easily pushed back in place).


Style: Stitches Squares
Purchased from: ebags
Exterior dimensions: 30.5" x 18.5" x 10.6"
Linear dimension: 59.6" (151 cm)
Weight: 5 lbs, 7 oz (2.5 kg)
** I have not tested this suitcase yet **
Pros: Wheels seem more solid than The Lite, comes in a variety of colors
Cons: Nearly a pound heavier than The Lite