new to this world: keyboard or synth?

Well, first of all - stay away from the MM6.

It's a hybrid keyboard that tries to be a synth and a workstation but fails miserably in both.

Keyboards are mainly devided into Arrangers, Workstations and stage/home pianos.

Arranger keyboards mostly (except high-end gear) have onboard speakers and
styles you can play along with. Most of them are mainly toys or mid-range keyboards
that do not focus on sound manipulation and editing. So don't expect anything much from those if you want to be able to edit and tweak your sounds.

Examples: Yamaha's PSR series, Roland GW, Korg Pa - Almost all of them come in 61key version. There are a few of them in 76key versions.

Workstations on the other hand have full sound manipulation that enable you to do
almost anythnig you want. They don't have styles you can play along with, but they
do have arpeggiators that can give you a basic beat to play along with.
The main feature of Workstations is the option to mix and layer several sounds together (4-8-16 different sounds playing together)

Examples: Yamaha Motif, MO, Korg Trinity, Triton, TR; X50; m50, m3, Roland Fantom, Juno
Workstations come in 61/76 key versions and 88 hammer weighted keys

Stage/home pianos, as the name suggests, have 88 piano style keys - meaning they
have hammer mechanics giving you the best feeling you can get for playing the piano itself. If you want the closest feeling you can get of playing the real thing you will want the stage piano.

They usually don't have much sounds on them, and don't give you the option of editing them very much, but the sounds that are onboard sound superior.

Examples: Yamaha P-series (P140/155), CP series (CP33, CP300, CP50, CP5, CP1), Roland RD series, Kawai ES, MP...

Stage pianos come in 88 progressive/balanced hammer keys. Meaning bottom keys
are heavier then the ones on the top - emulating the strings in the real piano

Now... when you decide what type of keyboard you want - we can take the next step
of trying to find the one you can buy for the money you have

GW7 is an arranger, and the CS6x is basically made for electronic music.
So out of those 3 the LE would be a better option.

If you run into a classic Triton don't hesitate for a second on buying.

Triton LE is a very stripped version of the Triton. Plasticky keys, no touch screen,
and only one IFX compared to 5 on the triton.

Also, I would recommend the Trinity even though it's old, but even today it sounds way better then the LE,
and has even more IFX then the triton!

The only problem is the lack of poliphony (32 compared to 64)...

It's simple - If it has styles you can play along with - it's NOT a full workstation.
Try splitting 4 sounds and layer them across the keyboard

Most Arrangers (even if they clame to be workstations) give you an option of "double"
or "layer" sounds that just double the right part of the keyboard (left part is saved for playing styles).

What if you want to have 3 sounds, 2 of which overlap?
You won't be able to do it

But, the bottom line always has to be the fact what YOU want and need from a keyboard.

Well... he made videos on almost every workstation available - meaning - you almost can't go wrong hehe

I guess it's good if you want to poke around the keyboard at home. If you want to create your own sounds and combis then no - cause you can't do that on an arranger.

Out of those keyboards - i'd go for the X50.

It's built cheap but it has much more options and better sounds then the rest of the keyboards you mentioned.

MM6 has no editing options whatsoever (not counting those knobs), and you can't
mix sounds apart from layering 2 of them together.

Juno Di has decent sounds but i don't like Roland cause of its limited capabilities...
You can get much more from other brands for the same money.

And as i already said - GW7 is primary an arranger keyboard so it's more style oriented.

X50 is basically the same as the TR except it doesn't have a sequencer (you will need to use the PC for recording stuff),
no sampling (you can't load new samples - but you can load edited sounds, and you can find LOADS of those around the internet), a bit
smaller screen, and it's keybed is cheaper a bit.

On the other hand - it's rediculously lightweighted which makes it very easy to carry around.

So, when it comes to sounds and capabilities the X50 (link) is the same as the TR (link), making it probably the best entry-level synth.

It's not a full sequencer. I think it records 8 tracks + pattern, where you can't record tempo changes or change only some parts of the track.

But do you really want to sacrefice the sound quality and combi creation
for a lousy sequencer? There are tons of freeware programs you could use for
audio recording or sequencing

In any case - go and try all the keyboards