What are some alternatives?
When comparing XML-Sitemaps.com and Screaming Frog SEO Spider, you can also consider the following products
DYNO Mapper - Create Sitemaps with the DYNO Mapper Visual Sitemap Generator.
Netpeak Spider - A desktop tool for fast and comprehensive technical audit of the entire website.
WonderWebWare Sitemap Generator - Sitemap Generator is freeware program that will help you to automatically generate site maps for google, bing and yahoo in their respective file formats.
Moz - Backed by industry-leading data and the largest community of SEOs on the planet, Moz builds tools that make inbound marketing easy.
GlooMaps - Create your visual sitemap on the go - easy peasy
SEO Crawler - A web-based crawler with real-time crawl feedback.