Of the 3 which should I buy

Based on the analysis, I would recommend buying Fortinet (FTNT).

1. **Consistent Growth**: Fortinet has shown consistent growth in its revenue, which is a positive indicator of the company's financial health and potential for future growth.
2. **Strong Financial Performance**: Fortinet's financial performance is robust, with a significant increase in subscription revenue and a gross profit of $180.0 million for the quarter. The company's revenue growth rate of 13% in Q3 is respectable.
3. **Strategic Positioning**: Fortinet's strategic positioning in the network security market, coupled with its innovative solutions, gives it a competitive edge. The company's focus on cloud-native security solutions and its partnership with Zscaler to enhance security and cloud capabilities position it well for future growth.
4. **Market Recognition**: Fortinet's stock has outperformed the Technology Select Sector SPDR Fund's rise, indicating market recognition of the company's potential.
5. **Financial Stability**: Fortinet's financial stability is reflected in its market capitalization of $74.4 billion, which classifies it as a large-cap stock.

While Rubrik (RBRK) has shown strong revenue growth and strategic partnerships, its higher revenue growth rate is partly due to a lower base effect, and it has a history of operating losses. Zscaler (ZS) has a lower growth rate in Q3 and a smaller revenue base compared to Fortinet and Rubrik. Therefore, Fortinet appears to be the best investment option among the three based on the provided analysis.