Fundamental analysis only!
TLDW;
What makes the 2018-2019 bubble more bearish:
More scams (shitcoins - ponzis - cloud mining scam - giveaways)
Big shitcoin increase (too many shitcoins - all fighting each other for liquidity)
Shitcoin inflation (Too many premined shitcoins / ICOs - no fairness)
Easier to short (Way easier for people to short BTC etc, because they don't believe in them - sucking fiat value out)
Cash settled futures (Big players got in early and had this all planned - Also Cash settled futures suck liquidity from spot markets
Lots of new scam exchanges and fake volume (Some of these exchanges might be stealing coins from people or trick them to buy scam coins)
Bubble in a bubble in a bubble (BTC - ETH - ICOs all fueled each other. First Bitcoin created interest in Ethereum, which then created interest for ICOs, which held Ethereum, which went up and then people took profit into Bitcoin - Essentially a leveraged bubble!)
ETH. FIAT and Stablecoin pairs (Bitcoin's price is partially affected by people using it for speculation. Bitcoin also drives this market. So when it is used less / has lower price, shitcoins deflate too! Also arbitrage sucks money out, as there are too many pairs / exchanges, so liquidity is fractured)
Dummer money got in (Like Crypto Cobain said, the IQ of people getting in after each bubble is lower... Why? Because back then it was harder to get into Bitcoin. People had to be more technical and educated to understand it).
Mt. Gox coins being sold in the market (Mt. Gox 'locked' coins started hitting the market, something that didn't happen in 2014-2015)
Back then the market cap was much smaller and there way more lost coins as a percentage (also GBTC had just launched and its 'locked coins' were a big percentage of the total amount)
Stablecoin wars (fractured liquidity and people selling 1$ for less - Millions lost by retail that was gained by malicious players)
Hash wars (Bcash split - liquidity crunch as well as Bitcoin being dumped for hash power)
Finally in 2013 there was an 80% correction. So the 13 to 1200 rally wasn't done in one go. It took a big break before the last big rally.
What makes the 2018-2019 bubble more bullish:
No Mt. Gox collapse - No Willy (the rally was legit, I don't buy the : Bitfinex printed Tether out of thin air FUD). So the rally was organic and real, without having a big exchange collapse.
More Liquidity and on ramps (many good, regulated and unregulated exchanges, along with many other ways to buy Bitcoin like ATMs, vouchers, etc)
Improved custody and security (Hardware wallets, custodial solutions like Gemini, Coinbase, BitGo and Casa Hodl)
Many OTC desks and Indices (Easier to buy/sell big amounts of coins without affecting the spot market a lot)
Big boyz getting in (Bakkt, ErisX and even the probability of an ETF being approved)
Crypto funds (back then there weren't many, if any approved crypto funds. Most got approved in 2017-2018-2019)
Regulatory clarity (in 2014 there was a lot of fear Bitcoin could be banned etc. Now it is legal and clearly defined in many countries like the US, EU, Japan and South Korea)
Better mining (More efficient mining, along with liquid options to hedge, more decentralized and with bigger-long term players getting in)
Less inflation (Most big coins like Bitcoin, Litecoin and Ethereum have smaller inflation rates than they had back then)
Financial products (Bitmex, Cryptofacilities/Kraken, Huobi, Bitflyer, OKex, Deribit and LedgerX offer liquid futures and options products)
True believers own more (The hodlers, the hodlers of last resort, the ones that truly believe in this game, who are now more certain than they were back then - forks also helped true Bitcoiners to increase their Bitcoin holdings by holding Bitcoin!)
25-30B got into ICOs (Just the shitcoin market alone bottomed at 40B, out of which 2.5B was in stablecoins. Some of it has gotten back into Bitcoin or shitcoins)
More talent and money (People that work in this industry probably reinvest some of their gains back into the market)
Way more good educational material (Back then our understanding was not as great and good information wasn't easy to find)
Shitcoins provide a lot of free marketing and education to Bitcoin by proxy, as well as provide Bitcoin with a clear use case - Shitcoin speculation!
Crypto borrowing - Use Bitcoin/Shitcoins as collateral to get fiat, without having to sell your coins!
Crypto lending - Earn money by lending your coins/fiat for people to trade with it (Bitfinex, Poloniex, Liquid)
Bitcoin/Shitcoin Utility - Joinmarket, Lightning, Maker DAO, Masternodes, Staking (Holding crypto to make more... Crypto by providing specific services, essentially restricting the supply) - I truly believe that Staking (DPoS, PoS, Masternodes etc will drive the next bubble really high. Projects like Loom, Maker, Edgeless, Augur, Dash, Ren etc make me believe that there is a lot people that will get in because of this.
Decentralised trading tools for traders (Bisq, Liquid, Ren, DEXs, Stablecoins)
Even more lost coins, Bitmex insurance fund growing and ICOs still holding ETH (lol-lol-lol)
Central banks have take risk away from the markets, by lowering rates and printing a lot of money. But this has also lowered the returns investors expect... Which makes many investors turn into more risky investments. Why risk 100% of your capital for 5-10% returns on junk bonds, and not risk 100% for 1000-10000% by just doubling/tripling your risk? More QE is coming and the total money supply has significantly expanded since early 2015.