I've been trying to figure out if it makes sense to use SSRS 2012 with PowerView vs using SSRS 2008.
I've following questions:
I can address the overall question but not the first two bullet points specifically as I have not used Sharepoint enough to give the version differences on it.
Powerview from everything I have ever done is a dll that allows a report like object to be created as an add on to Excel. These objects can then be hosted in Sharepoint in a library. The downside is you need to have the dll's and the add on to Sharepoint to use it. As far as I know you are committing to user's going to SharePoint with this option. They do make it kind of neat though as you generally make what I believe they call a 'PowerPivot' which is just like a client dataset made in the Excel file that you report off of. This option is good for a shop that works with Sharepoint Extensively. I have not heard of too many places using it for client facing front ends or external reporting.
SSRS's newest invocation is SSRS 2012 which from everything I have seen in development is the EXACT SAME THING as SSRS 2008R2 except they put a 2012 in the namespace. There may be minor tweaks on naming and intellisense and under the hood things but the langauge is almost identical. Saying that SSRS 2012 is free with advanced tools for SSRS now and can also port to most front ends you would want: HTML in a form talking to it's service, ASP.NET, a client app like WinForms or WPF. You basically created and host reports and you can access them anywhere.
The real question for most people is: "Which reports look cooler and are easier to use?" I would go with SSRS, but know it is more of learning curve of understanding SQL and a little bit of xml and Visual Studio(very light). However Powerview is more graphical with it's parameters and options to an end user and has highlighted some things it can do with mapping interactivity that SSRS cannot do. The biggest detractor for SSRS IMHO is two things:
Saying all that I still like SSRS better. It tends to handle large datasets when PRESENTING them better. Not necessarily all the time at getting them as the PowerView optimizes the set locally but at the expense of huge excel files. Sort of like psuedo cubes. They are fast, but you have a big file size for that expense. But with a lot of data they tend to be clunky as they are Excel based. Yes the query at the end will return faster but you have a huge file. When in reality if you are skilled at SQL SERVER you could be creating a Report Warehouse that is well indexed off of metrics and a cube as well to do this stuff for MANY REPORTS. SSRS is more for developers of TSQL, versus PowerView is more for analysts that know a little SQL but love Excel. They want a 'Select * from (table)' and then form the data, not they know how to do advanced groupings on their set first and then want to present a finished product to someone.