A slightly different view
I do not feel "simpler" is quite the right way to put it, unless we are talking about learning the oracle and how to use it. Then again in may cases I can see how others may feel this way depending on the particular oracle (Doreen Vertues cards are very easy to work with and learn).
I feel that Tarot is more complex and harder to learn in most compairative(sp?) cases, though not all.
Oracles are many times based around a culture and/or theme, like Fearies, Animals, Druidry, Native American Beliefs, extra. If one has a back round of interest and has learned a great deal about say "faeries" then it may be very easy just to piack up a deck and use from the knowledge and familaraty(sp?) one already has with the theme of the Oracle.
It has been my experience that Cultural oracles are more complex to learn though not always harder to use once studied and understud than tarot. For Tarot is based on a Christian/Catholic view of the world based around the 1400s or so. Where as say... The Druid Animal Oracle is based off of beliefs and values of Celtic people who lived over 7,000 years ago and the Druid beliefs connected to them and the animals and some plants that reflected and made up an important part of their world.
This Oracle (DAO) has only 30 cards to learn, where as Tarot has 78 cards.
Tarot is divided in to Major 22 cards and Minor 56 cards that are farther divided into 4 suites (40 cards), plus the court (16) cards.
DAO has a lose structure the main being that the animals are divided into "groupings": there are 4 Elemental groups, Animals that are considared "Pairs",those that are "connected to faeries," , and so on... the only cards that might be consider major cards are the 4 dragons. In the book it list more possible "groupings," but incourages you to find patterns or groupings that come to you. Plus on many but not all the cards there are plants or flowers that are connected to the animal or symbols within that animal card. From these added features you get a idea and might imagine how detailed a reading can become.
As to types of readings from The Tarot or DAO, I am able to do advise and answer readings with both. So again it would depend on the Oracle. If asked I prefer reading with the DAO, though I still read with Tarot when seekers ask for its use.
Sorry that was so long, but hope that adds some insight.
Hopeful Purrrs,
CloeCat