I can't speak for glopol but I have done Lit, so this is obviously a biased view
Nonetheless, I can confirm Lit does help with some aspects of English, and I personally found the course really enjoyable.
Ultimately it will come down to what you want to do after school, and tbh your subject selection won't matter a great deal. You've got Methods and English which is about all you need for prerequisites (bar Chemistry for Med.) If you're considering Arts then you could take a Politics subject at Uni that will cover everything you've learned from Units 1-4. You'll also be able to specialise in certain areas (eg. Contemporary Political Theory or Global Environmental Politics are some offered at Melb.)
Of course your interest levels will determine your performance far more so than subject selection, and VCE English is easy enough to grasp conceptually w/o Lit.
edit: Just realised you're in Year 10; the English study design is set to change (as are a couple of other subjects) which basically means the format of some of the essays will change. There's a compulsory creative piece, amongst other things. It's probably marginally closer to Lit. so those skills might be of some use. Alternatively you might find the overlap tedious and repetitive.
A brief defense of Lit: Yeah there's not a lot of jobs out there... (pay no attention to the English major sobbing in her little corner) but that doesn't mean the subject is without merit. Lit teaches you to think in a way that not even English can; you're examining the language so closely it can give you headaches, you're tying in historical contexts and considering alternate views. I know it gets a bad rep for the "bullshit" but I found that's not really the case. The assessors are kinda cynical about students using flowery language to obscure poor ideas and development. To do well requires a mix of both creativity and analytical ability, and in the end you'll be rewarded with a thinking style few other subjects can offer.
Then again, glopol might offer the same advantage just with a more political angle. Idk, hopefully someone here will have done both and can comment.
One last thing:
PROS FOR GLOBAL POLITICS
- I know that the teachers are amazing
This will make a massive difference. It basically defined how I picked my Year 12 subjects since I was struggling too. For some people I know it doesn't make a difference; with a good textbook/study group/forum you can pretty much teach yourself if you're so inclined. But I found the teachers I had made a difference to both enjoyment and performance in a subject, so perhaps you could organise to talk with some department heads about their subjects (if your school encourages it?) Otherwise seek out some current year 11s and 12s if you know anyone and gauge their opinions.
You could always pick one of these up in Year 12 without Units 1/2 if Eco or Media don't turn out to be what you hoped for.
Best of luck!