I recall reading that thoughts - in general - are very favorable for upgrading from 105 to 205. I never had an Oppo product until the 205, so I cannot provide comparison info from first hand experience.
http://www.avsforum.com/forum/149-blu-ray-players/2821841-official-oppo-udp-205-uhd-blu-ray-player-o...
http://www.avsforum.com/forum/149-blu-ray-players/2821841-official-oppo-udp-205-uhd-blu-ray-player-o...