Or instead of reorg, will it be faster if I just rebuild index instead?
The answer to that question is a resounding OMG YES!!!! Even if you're in the Full Recovery Model. It also doesn't take much fragmentation for REORGANIZE to lose it's mind, either. If the fragmentation is "wide spread" regardless of how little logical fragmentation there is, it can seriously cost you in time, disk activity, and log file entries.
Having it take 2 days, though? That sounds a bit much but I don't actually know because not only have I not used REORGANIZE on a 78GB index before, I flat out stopped using REORGANIZE at all since Monday, 18 Jan 2016.
I've also done a shedload of testing over the years... logical fragmentation just isn't the problem that most people think it is especially with SSDs or OLTP systems that are mostly reading one row at a time. It can make the first load to memory on spinning rust pretty bad but, once in memory, it just doesn't matter.
Page density matters because it wastes memory but it doesn't hurt performance by much once in memory.
I've also proven that it's better to do no index maintenance than it is to do it wrong and, if you're using REORGANIZE, there's a seriously good chance you're doing it wrong (99.9% chance in my unmeasured humble opinion).
Ola has recently checked in a mod to his good code that checks for page density. I'd key my Index Maintenance on that instead of logical fragmentation with the understanding that REBUILDing a fragmented index can cause a ton of page splits on the morning after because it has not room to grow if you REBUILD fragmented indexes that have a zero FillFactor. There are two exceptions to that general rule... Sequential Silos, which fragment like crazy but never have page density issues, and "exploding broom tip" indexes ("Ever-Increasing" indexes that follow the quick pattern of Insert/Process/"ExpAnsive Update"). If you can't fix the latter so they don't fragment any more, then rebuild them with a 97% FillFactor so you know what they are and call it a day.
Just to repeat it again, it's actually better to not do any index maintenance than it is to do it wrong and about 98% of the world is doing it wrong because they follow supposed "Best Practice that aren't and were never meant to be. In fact, it turns out that they're a "Worst Practice" for most indexes and are the biggest reason why people insist that Random GUIDs are a fragmentation problem when, in fact, they're the very epitome of how people think an index should work (except for true append-only indexes).
Whatever you do, I strongly recommend that you simply stop using REORGANIZE until you know a whole lot more about what it doesn't actually do and the pain it costs you and your indexes while it's not operating like you might expect it to.