Cenkos described the move as 'a rapid move to a simpler future', as it repeated its buy rating on the stock.
'This is a welcome move, we believe, cementing the SLA business as a capital-light asset management business rather than a capital intensive life one,' the broker said.
'The business will be simpler to understand and value; it will retain the ownership and new business generation of the various platform businesses of the existing SLA business.'
Meanwhile BNP Paribas analyst Arnaud Giblat, who reiterated his outperform rating setting a target of 505p on SLA, saw the sale as a 'positive outcome' as it leaves a 'pure play asset manager with a better growth profile trading at 8xPE19E'.
Giblat added: 'We expect the capital generated from the acquisition to be deployed in buybacks and/or deals.'
SLA shares bounced on the disposal news, jumping 2.5% to 395.2p by 11am.
The deal includes the bulk of the life and pensions business. SLA retains its platforms and advice arm, 1825, which currently sit within the insurance division.
While Cenkos was surprised by the timing of the announcement, it said it was not wrong-footed by the direction SLA has chosen to take following last year's merger between Standard Life and Aberdeen Asset Management.
'Since the creation of SLA there has been a question as to the value of retaining the life & pensions business within a company which clearly was aiming to be a pure-play asset manager,' the broker said.
'There are clear merits to the disposal in simplifying the group from an investor’s perspective, and material benefits from simplifying the capital requirements as it is the capital intensive part of the business which is removed.'
It added: 'The market has long struggled to ascribe a full value to this business, we believe, and the simplification to a straight asset manager should aid perception.'
The total value of the deal is £3.24 billion, the bulk of which will be made up of cash. Standard Life Aberdeen will also take a 19.99% stake in Phoenix worth around £1 billion, forming a strategic partnership between the pair.
The decision to sell the business comes a little more than week after SLA lost a £109 billion mandate from Scottish Widows, which wiped 7.6% off the firm's share price.
Cenkos noted the deal can also be a 'potentially interesting' enhanced relationship with Phoenix.
The alliance will see SLA's investment division, Aberdeen Standard Investments, take on the running of around £158 billion of Phoenix's assets under management.
'The legacy insurance business was always a bit of an odd fit with the new look Standard Life Aberdeen,' Hargreaves Lansdown equity analyst Nicholas Hyett commented.
'Selling it off to Phoenix provides a cash injection and frees up capital while the 20% equity stake should keep the assets under SLA’s management, potentially adding more from elsewhere in the Phoenix portfolio. Mutual back-scratching is much in evidence, but it’s a sensible deal.'