I did this for about a year (0700 Vic-Padd, 1900 return) and swore by the bus, at least for the morning journey. Nearly always quicker and much more pleasant (could get a seat most of the time on the 36, less often on the 436 but this was before debendification). If there's a long wait (unusual) then a 16 will take you to the end of Praed St, about 5 mins walk from Paddington.
On the return the bus was definitely slower especially down Edgware Road. I would think that the roads are likely to be busier than at 7 and so the Tube might be quicker. Definitely Vic/Bakerloo though unless there's major problems on either, the Circle generally takes an age.
Depends on your priorities really - bus is more pleasant IMO but the Tube can be quicker at busy times. If it's a regular thing then you'll be able to try out all the options.
If it's a nice day then it's a pleasant walk - up to Buckingham Palace, then through Green Park, Hyde Park across to Clarendon or Albion Gate then through across to Paddington. Takes around 45 minutes at a reasonable pace.