Observations in order of importance:

1) If your Okna quote is from Windows on Washington, this is a slam dunk for you. Excellent company top to bottom.

2) If it is not from WoW, call them. They are on another level, I promise.

3) Be careful not to confuse an attempt to compare apples to apples products within brand hierarchy with actual quality and performance. There's not a direct correlation. For instance, as brand hierarchies go, the Okna 500 is probably more equivalent to the base Sunrise product than the others. With that said, and as WoW alluded to, it actually outperforms the highest Sunrise models thermally and structurally, and is indeed nicer to install.... A more "dummy-proof" installation increases your odds for a great finished product.

4) Regarding the effect of MI purchasing Sunrise, that remains to be seen. On one hand, I believe that Rickenz is correct for the most part. Same window, same plant, etc. OTOH, there have been some moves made in personnel and other areas, and plenty of speculation on what the future may hold. It's rare in my experience to see that type of "merger" without things changing significantly, even if not immediately. The story usually goes something like this: High end, "boutique" window manufacturer bought by larger, lower tier (quality and performance) company. While the buyer may be trying to get a slice of that higher end market, they will also implement many of the "lean" processes used on the builder grade stuff to improve the profit margins. Why pay $12.50 for this part when we can get one similar for $8. These options that sell low volume will be discontinued in the name of efficiency... etc, etc. All of these little things add up.

Is the V5000 a bad window? Heck no. As it stands today it's still one of the better windows on the market. That said, you have another option that is objectively superior, comes with a lower price tag, and doesn't have that level of uncertainty that exists with MI/Sunrise. Most importantly though, again, working with an excellent company to get this done is key, so going with WoW would be on the top of my list and carry the most weight.