What is the best keyword tool for SEO and PPC? Why?

From my experience, one of the best keyword research tools for both SEO and PPC is SEMrush. Here's why:

Comprehensive Keyword Database

SEMrush has a massive database of over 20 billion keywords across various industries and countries. This gives you access to extensive keyword data and suggestions.

Accurate Search Volume and Metrics

The tool provides reliable search volume, competition, cost-per-click and trend data for keywords pulled directly from Google and other popular search engines.

Keyword Difficulty Scores

SEMrush assigns a "keyword difficulty" score to each keyword based on factors like domain authority of ranking sites. This helps identify low-hanging fruit opportunities.

Keyword Grouping and Organization

You can organize keywords into lists, conduct a keyword gap analysis against competitors, and get content clustering recommendations - very useful for SEO.

PPC Keyword Research

For PPC, you can analyze ad copy, and see metrics like potential traffic, competition level and more to identify the most valuable keywords to bid on.

Reporting and Integration

The tool integrates well with Google Analytics, Search Console and other platforms. You can also generate professional keyword research reports easily.

While not cheap, SEMrush provides an all-in-one solution for in-depth keyword analysis for SEO and PPC campaigns. Other great options are Ahrefs, Moz and LongTailPro depending on your specific needs and budget.