It's all comes down to max efficiency, Shopify/WooCommerce 50%, Prestashop 100%, Magento CE 200%, Magento EE 200-500% (with external tools like Heiler). NetSuite is a 500% ERP, SAP ECC is 1,000%, Linnworks <200%. Most service providers/retailers change the base install - it reduces efficiency from the standard 200% - therefore most small business run at ~50% 'true' efficiency, Amazon are 1,400%, Google are 2,000%.
Previously during the 'good times' Google and corporates looked the other way allowing small business to over-optimise their efficiency thereby ranking higher. Now that growth is hard to find small business are being ranked on 'true' efficiency - that is the complete business revenue stream not any one area - IT is only 5%.
Which is the best ERP, you need to match across the board all the tools, putting SAP ECC (1,000%) with Magento CE (200%) will limit your online revenue to the lowest common denominator - yes some do it but growth will be a disaster. We run at 950% on Magento CE but they stripped all the inefficient parts out and replaced them with enterprise grade processes.
Embedded ERP, Linnworks, will all run <200%, SAP B1 200-500%, NetSuite ~500%, SAP ByDesign 500-800%, SAP ECC/Oracle Financials 1,000%. The whole point of ERP is to improve efficiency, but if you match it with the wrong middleware, make too many changes, have a customised ecommerce install, you are going to reduce not improve efficiency - that occurs in 95% of cases.
So if your Magento CE is low efficiency ~50% (many will be) then Embedded ERP will be fine, the next level are Linnworks but there are not many 200% ERPs - OpenBravo is probably the best choice. After that you get in to the larger companies such as NetSuite & SAP - choosing a no-name platform will again reduce efficiency - they won't have the optimised business process automation.
For us this is all very simple, we work at 500%+ levels, the consultants above us 1,000%+, almost everyone here will be running at <200% and most ~50% - at that level there are 1,001 ways to do the same thing so there's no right answer.
The lower the efficiency the more it is time based and growth is restricted by number of employees, the higher it is the more that is automated and the faster you can use compound growth as per the graphic -
https://twitter.com/Serpyre/status/526786661066477569 - ignore the HEIC part - annoying low efficiency solution!