Hi there,
We are partial to Manulife as it is one of our Dividend Bull List picks and think it has excellent growth opportunities in Asia. This will lead to one of the highest expected earnings growth rates in the industry (~10%). It is also the cheapest in the industry and the only trading below book value. You can see our report for additional details.
That being said, SLF is certainly an excellent option and is one of the best performers in the industry. Much like Manulife, it has attractive growth opportunities and earnings are expected to grow by 8% annually. It is however, more expensive than MFC.
One way to get exposure to IAG and GWO is to look at parent company Power Financial Corp (POW) another Dividend Bull List pick. Although POW is more than an insurer - it is an asset management company with exposure to other industries so this may not meet your needs.
Of note,
I own both MFC and POW (have for many, many years).