Both programming and data analysis skills are highly advantageous in the field of ecommerce. However, the most advantageous skill depends on the specific role and requirements within the ecommerce industry.

Programming Skills:
1. Website Development: Proficiency in programming languages like HTML, CSS, JavaScript, and frameworks like WordPress, Magento, or Shopify can help in building and maintaining an ecommerce website. This skill enables customization, optimization, and integration of various features and functionalities.

2. Mobile App Development: As mobile commerce continues to grow, programming skills in mobile app development (iOS, Android) become crucial. Developing a user-friendly and responsive app can enhance the customer experience and increase sales.

3. Automation and Efficiency: Programming skills allow for the automation of repetitive tasks, such as inventory management, order processing, and data synchronization. This streamlines operations, reduces errors, and improves efficiency.

Data Analysis Skills:
1. Customer Behavior Analysis: Understanding customer behavior through data analysis helps in improving user experience, personalization, and targeted marketing. Analyzing data from sources like website analytics, customer surveys, and social media insights can reveal valuable insights for optimizing the ecommerce platform.

2. Sales and Revenue Optimization: By analyzing sales data, trends, and customer preferences, data analysis can identify opportunities for upselling, cross-selling, and pricing strategies. It helps in optimizing product offerings, promotions, and pricing to maximize revenue.

3. Supply Chain Management: Analyzing data related to inventory levels, demand patterns, and supplier performance can optimize the supply chain. This ensures efficient inventory management, reduces stockouts, and minimizes holding costs.

Ultimately, a combination of programming and data analysis skills would be the most advantageous. For example, programming skills can be used to develop a recommendation engine on an ecommerce website, while data analysis skills can be utilized to analyze customer preferences and behavior to improve the accuracy of recommendations.

References:
1. Shopify: https://www.shopify.com/
2. Magento: https://magento.com/
3. WordPress: https://wordpress.org/
4. "Data-Driven: Creating a Data Culture" by Hilary Mason and DJ Patil
5. "Python for Data Analysis" by Wes McKinney