Unlike Wave, FreshBooks, or QuickBooks, Invoice-Generator.com isn't a stripped-down entry point to a bigger paid platform — it's genuinely built to be a simple, free PDF invoice maker for small business, and it's been the default answer to 'free invoice generator, no signup' for a long time for good reason.
The real difference is what happens around the invoice, not the invoice itself. Invoice-Generator.com nudges you toward accepting online payments through its integrated payment processing, which adds a transaction fee if a client pays that way. SMBkits' generator has no payment collection built in at all — it produces the PDF, and how you get paid is entirely up to you and your client, with no processor sitting in between.
Both tools are functionally excellent for the core task: business details, client details, line items, tax and discounts, instant PDF download. If you want the option of a client paying online directly through the invoice, Invoice-Generator.com's integration is convenient. If you'd rather keep payment collection completely separate — a bank transfer, a check, a payment link you already use — SMBkits' version stays out of that decision entirely.
Either way, you're choosing between two free, no-account online invoice makers rather than choosing between free and paid — which is the more important thing to know if you've been comparing this category against QuickBooks or FreshBooks instead.