If I were playing you, neither one would be a detraction visually.

The cream one does look a bit oversized. Noticeable enough in the picture that it might be noticeable on the table top. Maybe not. The color makes it hard for me to see much of the details so it is difficult to tell if any detail would significantly stand out due to size.

The grey one doesn’t look bad at all. I doubt I would notice anything of consideration once painted. (Note: I don’t think the first one looks bad…it simply seems ‘off’ in scale to the body from the picture.)

Thank you! 

The creme ones actually scale better with Marines. When I buy some Scouts, I might use these heads on them.

If I can find a replacement for Green Stuff (my old GW supplies finally ran out), I might be able to make a neck using the second set of heads. Right now they all look downward.

I might have to change my helmet idea for the Sergeant. I kinda like the bald guy with the Nightvision Goggles. 

The creme to me looked a bit big, the grey looks a better fit. The head with night vision goggles looks cool.

Creme heads are too big. Grey are fine. But why you don't like kasrkins heads? There is heads with gasmasks which looks good. Also if you cut off filters you get almost same heads as your grey but fitting perfectly

Ah.  I see what you mean about the head tilt.
 

You can usually find Kneadatite in hardware stores and there are several places to buy it online if it’s not carried locally. It’s green stuff but sold in larger quantities/lower price per inch. I ordered online last time, but picked it up in Lowe’s or Home Depot before. It’s used to seal pipes.