Quick verdict
Composer is the cleaner choice for investors who want to create and automate rules-based portfolio strategies. TrendSpider is the stronger choice for traders who want charts, scanners, alerts and backtesting in one technical-analysis environment.
Building strategies
Composer focuses on composing systematic strategies from logical building blocks and running them as automated investment workflows. TrendSpider gives users a wider trading-analysis toolkit for defining, testing and monitoring technical conditions.
Charting and market analysis
TrendSpider has the advantage for chart-centric traders because visual technical analysis is fundamental to the product. Composer is less about living inside charts and more about defining portfolio logic.
Automation
Composer's proposition is closer to hands-off systematic portfolio execution. TrendSpider automates analysis, testing and alerts and can form part of an automated workflow, but the product serves a broader research role.
Which should you choose?
If your goal is systematic portfolio automation, start by evaluating Composer. If your goal is technical strategy development and active market analysis, TrendSpider is likely the more natural fit.