Well right off the bat, since you are new to Liferay, you might now be aware of the fact that the architectural changes to the product between 6.2 and 7.0 are -- let's say ... significant 
. I think most would agree, once they get over the initial frustration of change, that the changes are for the better and the direction taken will mean an even better product in the future -- but you should probably factor in some extra pain of migrating the plugins. There is a new mechanism for doing it based on OSGI which adds some complexity, but Liferay has also moved away from ANT using now Gradle instead. Maven is still available though if you are more comfortable there.
Moving from 6.2EE to 7.0 CE is not advisable though. The CE version of Liferay has some pretty significant pieces stripped out of it. These pieces are not things that can't be resolved, but gone are the days, for example, of just spinning up two CE servers and having them cluster on their own with just a few property settings. Other features that you may have been using, like Audience Targeting, are no long offered in the CE stream starting with 7.0 -- that was heart braking for me, and I am sure some others as well.
In the 6.2 and earlier versions of the product there were only really a few differences between EE and CE. Opting for EE is a great idea for up to dat security fixes, hot patches for bugs and of course. support from Liferay and their partners. 7 is a whole other story though. The EE version has been rebranded as DXP and from what I understand licensing is now more modular. You have the foundation piece (which I understand is the core) and then the other peices are managed separately (licensed separately even? I'm not sure...). The big changes I referenced above though, in particulay the cluster support, means the CE probably isn't an option in an enterprise deployment.
My advice to you would be this. If you are planning an upgrade, license DXP, don't try to move to CE. Personally, I feel Liferay as a organization has very fair and reasonable costs. If you compare what Liferay charges in licensing to their big competitors (Oracle, IBM, etc) they're a fraction of the cost. On top of that you have a much better product (though I have some bias -- I consider myself an unofficial evangelist) and better yet, a product that understands the needs of developers and really caters to them.
If money really is a pain point, then you could consider a mid point between a DXP infra and a CE infra. Some clients I have worked with will opt for a CE Development and QA environment, but then for UAT and PROD they license the EE (DXP) versions. With this model you can recognize some cost savings (with the tradeoff of course of those environments not being part of the support contract you have with Liferay) while at the same time mitigating security and bug issues you might encounter in PROD.
Hopefully this helps answer some of your questions -- if you have any additional questions, just fire'em back.
. I think most would agree, once they get over the initial frustration of change, that the changes are for the better and the direction taken will mean an even better product in the future -- but you should probably factor in some extra pain of migrating the plugins. There is a new mechanism for doing it based on OSGI which adds some complexity, but Liferay has also moved away from ANT using now Gradle instead. Maven is still available though if you are more comfortable there. Moving from 6.2EE to 7.0 CE is not advisable though. The CE version of Liferay has some pretty significant pieces stripped out of it. These pieces are not things that can't be resolved, but gone are the days, for example, of just spinning up two CE servers and having them cluster on their own with just a few property settings. Other features that you may have been using, like Audience Targeting, are no long offered in the CE stream starting with 7.0 -- that was heart braking for me, and I am sure some others as well.
In the 6.2 and earlier versions of the product there were only really a few differences between EE and CE. Opting for EE is a great idea for up to dat security fixes, hot patches for bugs and of course. support from Liferay and their partners. 7 is a whole other story though. The EE version has been rebranded as DXP and from what I understand licensing is now more modular. You have the foundation piece (which I understand is the core) and then the other peices are managed separately (licensed separately even? I'm not sure...). The big changes I referenced above though, in particulay the cluster support, means the CE probably isn't an option in an enterprise deployment.
My advice to you would be this. If you are planning an upgrade, license DXP, don't try to move to CE. Personally, I feel Liferay as a organization has very fair and reasonable costs. If you compare what Liferay charges in licensing to their big competitors (Oracle, IBM, etc) they're a fraction of the cost. On top of that you have a much better product (though I have some bias -- I consider myself an unofficial evangelist
) and better yet, a product that understands the needs of developers and really caters to them.If money really is a pain point, then you could consider a mid point between a DXP infra and a CE infra. Some clients I have worked with will opt for a CE Development and QA environment, but then for UAT and PROD they license the EE (DXP) versions. With this model you can recognize some cost savings (with the tradeoff of course of those environments not being part of the support contract you have with Liferay) while at the same time mitigating security and bug issues you might encounter in PROD.
Hopefully this helps answer some of your questions -- if you have any additional questions, just fire'em back.