Who each tool is really for
Bigin
Bigin positions itself as a deliberately small CRM from a very large software family. The proposition is restraint: a pipeline, contacts, activities and a clean mobile experience, without the configuration surface of a full platform. It suits micro and small businesses in India that have outgrown a spreadsheet but do not want a system that needs an administrator, and it benefits from sitting near a wider ecosystem if you later need more.
Kylas
Kylas positions itself as a sales CRM built for growing Indian businesses, with broader functionality and a visible emphasis on onboarding, training and support. It suits teams that have moved past a handful of people, have several products or territories, and want someone to sit with them during rollout rather than pointing them at documentation.