Fòram na Gàidhlig

I am looking at a question, and the implication is that one of the following sentences is wrong - or perceived to be "wrong" to someone on Aonad a Naoi of ACI at Sabhal Mòr Ostaig:

Bu toil le mo nighean coimhead air balaich Ross County a’ cluiche ball-coise
Is toil le mo nighean coimhead air balaich Ross County a’ cluiche ball-coise

Now, the first is definitely correct:

Bu toil le mo nighean coimhead air balaich Ross County a’ cluiche ball-coise - My daughter would like to watch Ross County boys playing football

So there must be something up with:

Is toil le mo nighean coimhead air balaich Ross County a’ cluiche ball-coise

My only thought is that they want us to put in "a bhith", however, I thought it worked with AND without i.e.

Is toil le mo nighean coimhead air balaich Ross County a’ cluiche ball-coise - My daughter likes to watch Ross County boys playing football
Is toil le mo nighean a bhith a' coimhead air balaich Ross County a’ cluiche ball-coise - My daughter likes watching Ross County boys playing football

Or am I missing some difference between 'S toil and Bu toil when it comes to dropping a'/ag i.e. is the coimhead after bu toil "to watch", but the coimhead after 's toil is simply the plain verbal noun "watching"?

Ok, I'll answer this, Perhaps it seemed like a trick question, it wasn't. In this week's class the answer was what I expected it would be. As far as SMO are concerned, you use a bhith with 'S toil. You can use it without i.e.

'S toil leam ruith sa choille
'S toil leam a bhith a' ruith sa choille

...are both grammatically correct but the second is seen as more correct/normal.

Don't shoot the messenger.

That's the standard answer, and it works as far as it goes. What is missing is the reasoning behind it, and the nuances that the two options permit.
This is my take on it.

Take a verb like peanteadh.

'S toil leam peantadh vs. 's toil leam a bhith a' peanteadh.

The first one means I like the idea or concept of painting - whether I actually do it or not is not said, and the absence of a bhith implies to a certain extent that I do not. In other words, I may like it as an art form, I may like it as a school subject.
But I am not saying whether I do it myself. I'm staying neutral, or it's irrelevant.
Dè as toil leat aig an sgoil? 'S toil leam spòrs, 's toil leam peantadh, cha toil leam Beurla.... agus 's toil leam a bhith a' snàmh gach Dihaoine, gu mòr mòr!
The a bhith form basically says I like and I do it.
You're visualising doing it, with pleasure.

The verbal noun is a noun. The construction without a bhith mirrors the simple 'S toil leam ball-coise; 's toil leam càise, 's toil leam fiolmaichean Eadailteach statements. Neutral statements, without stressing the engagement in the activity associated with these things.

The fact that Bu toil leam is "allowed" with the bare verbal noun has to do with the fact that it's the conditional, it would be nice but it's not happening, and it may not.
You could of course also say:
Bu toil leatha a bhith a' coimhead orra ...
- she would like to be watching them right now (but unfortunately she's doing her homework...).

Nuances and context are everything.

As I say, that's my take on it, after a long time of observation, and asking native-speakers for examples in various contexts. Others may have other angles.

Yep, understand that. So going back to the original post...there was nothing grammatically wrong with either of the phrases:

Bu toil le mo nighean coimhead air balaich Ross County a’ cluiche ball-coise
Is toil le mo nighean coimhead air balaich Ross County a’ cluiche ball-coise

It's just that SMO (for now) are choosing to focus on 'S toil + a bhith.

They're probably just focusing on that for now because they like doing things nice and sequentially and there's a wee bit more grammatical baggage that comes along with the non "a bhith" form once you start dealing with direct objects.

I didn't do ACI, but we were already expected to know what's going on there at the start of ACA so you'll be covering it soon I'm sure.

Aidh, sounds about right.

Still, whatever the reasoning, it's pretty iffy to set a "which of these is wrong" question where the "wrong" one isn't actually wrong.