The design for the bus terminal has been released, and it isn't good:
http://urbantoronto.ca/news/2017/07/blue-snake-first-look-upcoming-scarborough-centre-subway-station
Due to its incredible length of 400+ metres, and its placement relative to the station box, TTC customers will have to, once at terminal level, walk a distance of up to 223 metres to get to their buses. This takes about 2.7 minutes to walk (160 seconds). Assuming it takes 60 seconds to get from platform level to bus terminal level, total time from the subway train to the bus bay will take up to 3.7 minutes.
This is appears to be the single longest transfer on the subway system. Which is deeply ironic, since the entire point of the SSE was to eliminate an inconvenient transfer.
To compare the subway and the LRT plan, the subway now appears to leave commuters with a less convenient that is either as slow or slower than the LRT transfer would have been
Commuters travelling directly to Scarborough Town Centre (the mall) will have to walk from platform level to street level (with a vertical elevation significantly larger than the LRT offfered) and cross part of the existing STC parking lot. They'll then have to cross Borough Drive, likely at a signalized intersection (adding even more waiting time). And if you really want to nitpick, once inside the mall they'll have to cross the cineplex complex to get into the shops.
The LRT would've required a short climb down to ground level, and the station would've connected directly to the mall.
Commuters transferring from subway platform level to TTC busses will face up to a 3.7 minute (222 second) walk to their buses.
Conversely, commuters would have had to wait up to 139 seconds for the LRT, plus perhaps another 60 to 90 seconds of walking from the Scarborough Centre LRT platform to the bus platforms. So a transfer time of up to 222 seconds for the subway vs a transfer time of about 199 to 229 seconds for the LRT plan.
And of course, passengers that would've used Lawrence East, Midland, Centennial or Sheppard Stations face significantly longer travel times since their buses need to all travel to Scarborough Centre.
Irony aside, this will also have significantly negative ramifications for the ridership of this line. Passengers are already averse to transfers, and 3.5 minutes is worse than all TTC transfers, obviously discouraging use of this transit line.