I typically haven't seen a large premium for "name brand" tent. As others have indicated, the more expensive tents are typically made from more expensive materials (typically better performance vs weight) with higher quality construction.

In nice weather, anything will do. Many of us just cowboy camp (sleeping bag on top of a ground cloth) when the weather is nice. As others have indicated, the cheap tents typical show their flaws when you really want them to protect you.

Personally, I want a shelter that gives me the protection I need, leave me as connected to my environment as possible, and gives me a "just right" amount of protected space since too much is hard to set up, and too small makes in uncomfortable to manage in bad weather.

As to sleeping in a tent -vs- tarp in bear country... there have been some studies / analysis of bear encounters done over the last few years. I can't find them right now but my memory is that there was only a minor reduction of risk when using a tent -vs- open tarp. The much more significant issues where food (and other smelly things) being place away from sleep site, and that larger parties (>=3 is my memory) have a significant lower chance of an encounter.

I tend to recommend ultralight / tarptent type shelters.