Neither of those routes are step-free - there's no step-free access onto the Circle/District at Victoria, nor is there step-free access from the Southern half of the Circle/District platforms at Paddington. However, Thameslink to Farringdon and changing onto the Circle or Hammersmith & City should be step-free. Farringdon, I believe, has step-free access between Thameslink and the Circle/Hammersmith & City platforms via lifts (though I think you might have to use two sets of lifts, which might be irritating), and Paddington Northern half of the Circle/Hammersmith & City has lifts.
(There's confusion at Paddington because the Circle line uses two completely different sets of platforms depending on which direction you're coming from - the platforms from the northern half of the circle line shared with the Hammersmith & City, as opposed to the southern half of the circle line shared with the District, are step-free.)
Another option which requires a change of trains, if you're OK with routes that involve escalators but not stairs, is to get the Victoria line from Victoria (step-free) and change at Oxford Circus (step-free for same-direction interchange) onto the Bakerloo line to Paddington (which has escalators but not lifts).
Source: http://content.tfl.gov.uk/step-free-tube-guide-map.pdf and http://content.tfl.gov.uk/avoiding-stairs-tube-guide.pdf