Sounds like a reasonable decision to me
If you mean less work as in 'guess everything', specialist. Even <30 scores scale up to a respectable number. If you mean 'only do the work in class', I would still opt for specialist for the same reason. Past that it probably is around the same raw score (so spesh still comes out on top) and a matter of preference as to which you choose. For further you have to do very well to get above the higher 30s simply because there are people who take it because it is an 'easier' class - year 11s looking to get ahead, or others who do the other maths and already have a very strong foundation, or even some that only do further but work hard. You're
almost always going to do better with specialist - there's a very strong high-end cohort, but the low-mid isn't as competitive because a lot of people are scared away from spesh because it's 'the hard maths'. The only reason I would consider further over specialist at all is you find the content more interesting, or relevant to your life.
For your edit: Specialist, hands down. 35 is very achievable.