Every library has its strengths and weaknesses. The Orchestra is a tool for composition that can make a lot of work easier. It also helps to find ideas, especially since it offers many articulations for the strings.
The strings are not bad at all, some of them I like to use very much, especially in the lower registers.
Nucleus has an overall better, cleaner and clearer sound without noise, better legatos, solo instruments. Unfortunately there are some articulations missing which I replace with other libs (e.g. thrills for strings).
Both have their place on my macbook and I think the prices are justified.
The sound of the Iconica ensembles is very good, but I don't like the legatos, and the dynamic range is too low for me. They don't offer me anything I don't already have and so I decided against Iconica. It's also a matter of taste and they didn't hit mine.
I covered my needs for sketching (Symphobia 1-3, TO, Nucleus, BHCT). In principle, all areas are well covered (especially drum, string and brass libs), but there are always new tools that are an enrichment, such as Time Micro from Orchestra Tools. Drum and percussion libraries used to be my passion, but I've found my setup with which I'm absolutely happy. For this area it was easier than e.g. in the orchestra area.
The sound of the BBCSO appeals to me and I will probably order it too. So far EWHO and VSL Synchron-ized are my orchestral library, they are not sorted out either, but I also feel the need to try something new that sounds more modern and different. I like the tools of spitfire and OT that provide rhythmic textures, which is an enormous enrichment and breathes new life into it. I find the libs I have no worse, they are different. When someone asks me if I need new libs, I say no, I don't.
I will decide when more information is available.
Since I like to make experimental music besides classical music and heavy metal, there can't be enough possibilities.
Fortunately I don't have to worry about the budget. But if I had to calculate with every cent I would limit myself to 3-4 of the most important tools, think about exactly what I want to do beforehand and research exactly which librarys best serve this purpose. The choice in the years became frighteningly large, but I also see advantages in it.
The general best tool doesn't exist and I don't think it will ever exist. That's up to the users and fortunately the tastes are different.