Higher plans include more server resources (#1 factor in the WordPress optimization guide). Here’s the full comparison chart, but GrowBig gives you about 2x more server resources than StartUp, and GoGeek is semi-dedicated hosting which gives you even more. GrowBig and up comes with a free migration, staging, advanced caching, and ability to host multiple websites. GoGeek comes with priority support. Their cloud hosting is quite the price jump at $80/month.
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