Having used both Shimano Ultegra and Microshift 10-speed, Here are my observations:

The Microshift works fine, but I have no idea about longevity. I've only used it for about 500 miles, but there's no sign of wear. There is a lot of plastic in there, so I'm slightly worried. The shifts are positive, but slightly noisy- there's a real loud click when a gear is engaged.

The Ultegra I've used for about 10000 miles over the last 5 years. It still works, but it's getting sticky in cold weather- won't shift down sometimes, indicating dried-out lubricant. Otherwise, it has been flawless. Pretty good life. Neither is actually rebuildable like Campy brifters. The action of Ultegra is definitely more smooth and crisp- Microshift is probably about 105 or Tiagra equivalent in quality, definitely lower than Ultegra.

90 grams isn't enough to worry about unless you're a real weight-weenie. I made the decision between Microshift and Tiagra for the backup bike based mostly on cost, although if I needed 3x10 I would have gotten the Tiagra.