I've worked for both and so can be of some help. I've offered an answer to each of your questions below. Hope it helps!
- How does the culture differ?
Deloitte HC is a nicer place to work, smaller and more collegiate. There's definitely more focus on community and you'll feel part of something. Accenture felt too big, and the HC practice under-valued by the rest of the business
- Is there any difference in Work-Life balance?
Yes - on average you'll work less hours at Deloitte. Having said that, as you'll know, it all depends on the project and the extent to which the partner has been squeezed on the price of the job
- How do salaries compare at Senior Consultant / Manager Level?
Accenture pay better but you may be able to negotiate on entry to bring the Deloitte rate up to an ACN equivalent
- Is there any difference in career progression?
Yes, it takes longer in Deloitte due to the extra Senior Consultant grade. But if you're on for partner, eventually you'll be rewarded better at Deloitte as it's a partnership
- What type of work do each tend to specialise in?
Deloitte has a good organisation design practice and pedigree. I'd say Accenture is stronger in the HRT space. Both have decent strategic change teams
- Who are their main clients?
Can't speak for ACN now, but most Deloitte HC work is now in the public sector and financial services. Very little is sold in the consumer products, technology and media sector where I'd think Accenture is stronger