Holafly markets unlimited data plans. Simline focuses on transparent metered plans. Here's where each makes sense.
Metered, transparent plans with no throttling. You see your remaining GB; you only buy what you need.
Unlimited data marketing, but speeds are throttled after a daily cap in most countries. Higher price point.
Holafly's 'unlimited' is a marketing label, not a contract. If you actually use your data, metered Simline plans win on cost and transparency.