Defs agree that English will help you more in glopol and legal, and you may even find some of the stuff you cover in those two subjects can aid you in English (context, specifically) essays too. And you're right about Lit's subjectivity; whilst it is possible to work hard to a point where you can be certain of a 40+ score, often what separates high-end essays is the assessors' bias, unfortunately. English isn't quite so bad, and it's much more easy to grasp, so don't worry about not having done 1/2.
Technically re: scaling, English does down by one, Lit goes up by one or two depending on the year, but it's a really minor effect either way.
Generally if you don't
enjoy Literature as a subject, I'd say drop it. It was my favourite in Year 12, but even then I got so frustrated with the vague marking scheme and the way my grades would vacillates with no explanation. I guess teaching plays a role (since my teacher basically gave me two ticks and a 'good' on every essay I wrote - nothing more -.-) so if you know who the Literature teacher(s) will be next year, then you can factor that into your decision.
With regards to your Lit. score, do you tend to do better in Passage/Close Analysis, or the additional (eg. Adaption essays, Views & Values, Creatives) because the course is structured rather strangely. There are five SACs in Year 12, only one of which is what you'll be dealing with in the exam, so it's a deceptively difficult workload because what you do for the SACs doesn't realistically prepare you for the exam until late Term 3. A good teacher will keep up the Passage Analysis on the side, but it does involve a lot of effort on your part.
For English meanwhile:
1 Persuasive Oral SAC; worth very little & not on the exam, usually in the first few weeks of Semester 1
1 Language Analysis SAC in Semester 1
2 Text Response SACs; one in each Semester
2 Context Pieces; one in each Semester
And your exam:
1 Language Analysis
1 Text Response
1 Context
...so it's much more geared towards the end of year assessment.
Only downside I can think of for switching would be the temporary disorientation if you haven't done English since Year 10 (and in my experience, a lot of schools teach things badly from Year 10 and below, so there can be a steep learning curve for everyone once they get to the upper year levels) but you'll find a lot of your Lit skills to be transferable - particularly for the Language Analysis and Text Response essays - so that shouldn't be too much of a problem.
Let us know if you've got any questions about either course!

And there's a post
here that gives a general overview of both the 3/4s if you're interested.