Since you are interested in Samsung.
http://www.anandtech.com/show/6553/sandisk-ultra-plus-ssd-review-256gb/7
Most support personal don't understand much more of the matter than people in forums like this one, unfortunately.
If you want to understand the subject read stuff like on anandtech they had a few articles explaining in detail what GC and Trim does.
Generally there are differences in SSDs and somethings that are always true.
If there is enough space actually free than GC can do its magic well. You can rely on the firmware defined over provisioning or do it yourself by not partitioning a part of the drive. Old SSDs like from Sandforce started with 28% over provisioning. So even if you had it 100% filled with incompressible data it was only 2/3 full and overwriting LBAs works. Next they got down to 13% on consumer drives and is now at 7%. Curcial with the M4 is almost a 0%.
What they mean by GC usually is just non real time GC. But GC simply cannot possibly know what it is allowed to collect until an LBA is overwritten or a Trim command marks an LBA as deleted.
Put simple say you got 4 pages a 4 blocks (only to keep the example simple).
Your performance eventually sucks if you have to many small writes into empty space that used to be deleted.
-xx- -x-- xx-- xxx-
All GC does is (ie. when the SSD starts hitting a 85% fill level) to combine blocks of data so it got more full empty blocks.
xxxx ---- ---- xxxx
That is really all it does. Works fine with enough free space used to be provided by over provisioning.
Now if you have Trim and delete stuff the SSD knows that is deleted. It still needs to actually delete the data which it might not do right away.
-ee- -x-- xx-- xxx-
GC can go to work and do this when it feels like it.
---- ---- xx-- xxx-
Without Trim you can delete all you want the SSD doesn't know. You add maybe more data but the OS doesn't write it into the same LBAs. Eventually the drive will be practically 100% full all the empty space being over provisioning.
-xx- xxxx x-xx xxxx
If you want to write some new data and over write some old.
-xn- nnxx x-xx xxxx
It needs to read the second block before it can write to it.
kind of like
read xxRR save it in memory.
write nnxx write the extra n somewhere and mark the one as empty
-xe- nnxx xnxx xxxx
If there was Trim it could have just written in the empty first block because it already new maybe that that block is empty.
-ee- xxxx x-xx xxxx
write into the empty block
nnn- eexx x-xx xxxx
much faster.
The thing is SSD don't write to specific locations. They have a big tree in memory where they can see where there are empty cells and where there aren't. With small writes you inevitable and up splattering data all over. GC just cleans that up but it will always be less efficient if there isn't enough space to work with.
Most consumers write big files, often use Windows with Trim and thus drives like the M4, Samsung have practically no need for too much overprovisioning better to sell them as 256GB rather than 240. Intel is more conservative. Sandforce used to be too. Also Sandforce had once a firmware that was buggy with Trim but not anymore.
So generally there will be enough free space or too few random sprinkled small files. If all you save is movies you just won't have a problem. Overwriting xxxx is just as fast whether it is empty or not. It is only slower if there is a bit of data in it that must not be overwritten because you can only write by deleting the whole block and next write stuff and if you need to not overwrite a part of it you need to read it first and write it elsewhere.
Trim simply helps the whole process because you deal with a drive that is effectively only as filled up as it seems to you and as the OS reports. It doesn't matter how much over provisioning there is if you keep 20% free most of the time. Without Trim the drive may effectively be 95% filled even though it looks to you like a 40% full drive. But the performance is as if it was 95% full and not what it seems to you.
I used an M4 for a while (3-4 months) without Trim and it suffered horribly. I got a pretty write heavy workload (get about 20GB a day for some reason on average) and would not recommend using that drive without Trim. The Samsung should be quite similar in how it operates.
Sandforce has the benefit of compression as I believe the data cells not needed due to compressed data go effectively towards over provisioning. Small writes are quite often compressible. Sandforce simply stands a greater chance of being less filled than it should be.
Intel is different as they do GC usually immediately after writes and still use quite a bit of spare area.
This article explains the whole thing in more detail.
http://www.anandtech.com/show/2829
Trim doesn't hurt unless the firmware is broken and has a bug which none do nowadays. I would always enable it especially with Curcial/Toshiba/Samsung drives and Vertex 4
